# Heterojunction

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Interface between two layers or regions of dissimilar semiconductors

A **heterojunction** is an interface between two [layers](/source/Layer_(electronics)) or regions of dissimilar [semiconductors](/source/Semiconductor). These semiconducting materials have unequal [band gaps](/source/Band_gap) as opposed to a [homojunction](/source/Homojunction). It is often advantageous to engineer the electronic energy bands in many solid-state device applications, including semiconductor lasers, [solar cells](/source/Solar_cell) and transistors. The combination of multiple heterojunctions together in a device is called a **heterostructure**, although the two terms are commonly used interchangeably. The requirement that each material be a semiconductor with unequal band gaps is somewhat loose, especially on small length scales, where electronic properties depend on spatial properties. A more modern definition of heterojunction is the interface between any two solid-state materials, including crystalline and amorphous structures of metallic, insulating, [fast ion conductor](/source/Fast_ion_conductor) and semiconducting materials.

## Manufacture and applications

Heterojunction manufacturing generally requires the use of [molecular beam epitaxy](/source/Molecular_beam_epitaxy) (MBE)[1] or [chemical vapor deposition](/source/Chemical_vapor_deposition) (CVD) technologies in order to precisely control the deposition thickness and create a cleanly lattice-matched abrupt interface. A recent alternative under research is the mechanical stacking of layered materials into [van der Waals heterostructures](/source/Van_der_Waals_heterostructures).[2]

Despite their expense, heterojunctions have found use in a variety of specialized applications where their unique characteristics are critical:

- *Solar cells*: Heterojunctions are formed through the interface of a [crystalline silicon](/source/Crystalline_silicon) substrate (band gap 1.1 eV) and [amorphous silicon](/source/Amorphous_silicon) thin film (band gap 1.7 eV) in some solar cell architectures.[3] The heterojunction is used to separate charge carriers in a similar way to a [p–n junction](/source/P%E2%80%93n_junction). The [Heterojunction with Intrinsic Thin-Layer](/source/Heterojunction_solar_cell) (HIT) solar cell structure was first developed in 1983[4] and commercialised by [Sanyo](/source/Sanyo)/[Panasonic](/source/Panasonic). HIT solar cells now hold the record for the most efficient single-junction silicon solar cell, with a conversion efficiency of 26.7%.[1][5][6]

- *Lasers*: Using heterojunctions in [lasers](/source/Laser) was first proposed[7] in 1963 when [Herbert Kroemer](/source/Herbert_Kroemer), a prominent scientist in this field, suggested that [population inversion](/source/Population_inversion) could be greatly enhanced by heterostructures. By incorporating a smaller [direct band gap](/source/Direct_band_gap) material like [GaAs](/source/GaAs) between two larger band gap layers like [AlAs](/source/AlAs), [carriers](/source/Charge_carriers_in_semiconductors) can be confined so that [lasing](/source/Lasing) can occur at [room temperature](/source/Room_temperature) with low threshold currents. It took many years for the [material science](/source/Material_science) of heterostructure fabrication to catch up with Kroemer's ideas but now it is the industry standard. It was later discovered that the band gap could be controlled by taking advantage of the [quantum size effects](/source/Quantum_size_effects) in [quantum well](/source/Quantum_well) heterostructures. Furthermore, heterostructures can be used as [waveguides](/source/Waveguide) to the [index step](/source/Step-index_profile) which occurs at the interface, another major advantage to their use in semiconductor lasers. Semiconductor [diode lasers](/source/Diode_laser) used in [CD](/source/CD) and [DVD](/source/DVD) players and [fiber optic](/source/Fiber_optic) [transceivers](/source/Transceiver) are manufactured using alternating layers of various [III-V](/source/Semiconductor_materials) and [II-VI](/source/Semiconductor_materials) [compound semiconductors](/source/Compound_semiconductor) to form lasing heterostructures.

- *Bipolar transistors*: When a heterojunction is used as the base-emitter junction of a [bipolar junction transistor](/source/Bipolar_junction_transistor), extremely high forward [gain](/source/Gain_(electronics)) and low reverse gain result. This translates into very good high frequency operation (values in tens to hundreds of GHz) and low [leakage currents](/source/Leakage_current). This device is called a [heterojunction bipolar transistor](/source/Heterojunction_bipolar_transistor) (HBT).

- *Field effect transistors*: Heterojunctions are used in [high electron mobility transistors](/source/HEMT) (HEMT) which can operate at significantly higher frequencies (over 500 GHz). The proper [doping](/source/Doping_(semiconductors)) profile and band alignment gives rise to extremely high [electron mobilities](/source/Electron_mobility) by creating a [two dimensional electron gas](/source/2DEG) within a [dopant free region](/source/Intrinsic_semiconductor) where very little [scattering](/source/Scattering) can occur.

- *Catalysis*: Using heterojuntions as photocatalyst has demonstrated that they exhibit better performance in CO2 photoreduction, H2 production and photodegradation of pollutants in water than single metal oxides.[8] The performance of the heterojunction can be further improved by incorporation of oxygen vacancies, crystal facet engineering or incorporation of carbonaceous materials.

## Energy band alignment

The three types of semiconductor heterojunctions organized by band alignment.

[Band diagram](/source/Band_diagram) for straddling gap, *n*-*n* semiconductor heterojunction at equilibrium.

The behaviour of a semiconductor junction depends crucially on the alignment of the [energy bands](/source/Energy_band) at the interface. Semiconductor interfaces can be organized into three types of heterojunctions: straddling gap (type I), staggered gap (type II) or broken gap (type III) as seen in the figure.[9] Away from the junction, the [band bending](/source/Band_bending) can be computed based on the usual procedure of solving [Poisson's equation](/source/Poisson's_equation).

Various models exist to predict the band alignment.

- The simplest (and least accurate) model is [Anderson's rule](/source/Anderson's_rule), which predicts the band alignment based on the properties of vacuum-semiconductor interfaces (in particular the vacuum [electron affinity](/source/Electron_affinity)). The main limitation is its neglect of chemical bonding.

- A *common anion rule* was proposed which guesses that since the valence band is related to anionic states, materials with the same anions should have very small valence band offsets. This however did not explain the data but is related to the trend that two materials with different anions tend to have larger [valence band](/source/Valence_band) offsets than [conduction band](/source/Conduction_band) offsets.

- Tersoff[10] proposed a *gap state* model based on more familiar [metal–semiconductor junctions](/source/Metal%E2%80%93semiconductor_junction) where the conduction band offset is given by the difference in [Schottky barrier](/source/Schottky_barrier) height. This model includes a [dipole](/source/Dipole) layer at the interface between the two semiconductors which arises from [electron tunneling](/source/Electron_tunneling) from the conduction band of one material into the gap of the other (analogous to [metal-induced gap states](/source/Metal-induced_gap_states)). This model agrees well with systems where both materials are closely lattice matched[11] such as [GaAs](/source/GaAs)/[AlGaAs](/source/AlGaAs).

- The *60:40 rule* is a heuristic for the specific case of junctions between the semiconductor GaAs and the alloy semiconductor Al*x*Ga1−*x*As. As the *x* in the Al*x*Ga1−*x*As side is varied from 0 to 1, the ratio Δ E C / Δ E V {\displaystyle \Delta E_{C}/\Delta E_{V}} tends to maintain the value 60/40. For comparison, Anderson's rule predicts Δ E C / Δ E V = 0.73 / 0.27 {\displaystyle \Delta E_{C}/\Delta E_{V}=0.73/0.27} for a GaAs/AlAs junction (*x*=1).[12][13]

The typical method for measuring band offsets is by calculating them from measuring [exciton](/source/Exciton) energies in the [luminescence](/source/Luminescence) spectra.[13]

## Effective mass mismatch

When a heterojunction is formed by two different [semiconductors](/source/Semiconductor), a [quantum well](/source/Quantum_well) can be fabricated due to difference in [band structure](/source/Band_structure). In order to calculate the static [energy levels](/source/Energy_level) within the achieved quantum well, understanding variation or mismatch of the [effective mass](/source/Effective_mass_(solid-state_physics)) across the heterojunction becomes substantial. The quantum well defined in the heterojunction can be treated as a finite well potential with width of l w {\displaystyle l_{w}} . In addition, in 1966, Conley et al.[14] and BenDaniel and Duke[15] reported a [boundary condition](/source/Boundary_condition) for the [envelope function](/source/Envelope_(mathematics)) in a quantum well, known as BenDaniel–Duke boundary condition. According to them, the envelope function in a fabricated quantum well must satisfy a boundary condition which states that ψ ( z ) {\displaystyle \psi (z)} and 1 m ∗ ∂ ∂ z ψ ( z ) {\displaystyle {\frac {1}{m^{*}}}{\partial \over {\partial z}}\psi (z)\,} are both continuous in interface regions.

Mathematical details worked out for [quantum well](/source/Quantum_well) example.

Using the [Schrödinger equation](/source/Schr%C3%B6dinger_equation) for a finite well with width of l w {\displaystyle l_{w}} and center at 0, the equation for the achieved quantum well can be written as:

- - − ℏ 2 2 m b ∗ d 2 ψ ( z ) d z 2 + V ψ ( z ) = E ψ ( z ) for z < − l w 2 ( 1 ) {\displaystyle -{\frac {\hbar ^{2}}{2m_{b}^{*}}}{\frac {\mathrm {d} ^{2}\psi (z)}{\mathrm {d} z^{2}}}+V\psi (z)=E\psi (z)\quad \quad {\text{ for }}z<-{\frac {l_{w}}{2}}\quad \quad (1)} - − ℏ 2 2 m w ∗ d 2 ψ ( z ) d z 2 = E ψ ( z ) for − l w 2 < z < + l w 2 ( 2 ) {\displaystyle \quad \quad -{\frac {\hbar ^{2}}{2m_{w}^{*}}}{\frac {\mathrm {d} ^{2}\psi (z)}{\mathrm {d} z^{2}}}=E\psi (z)\quad \quad {\text{ for }}-{\frac {l_{w}}{2}}<z<+{\frac {l_{w}}{2}}\quad \quad (2)} - − ℏ 2 2 m b ∗ d 2 ψ ( z ) d z 2 + V ψ ( z ) = E ψ ( z ) for z > + l w 2 ( 3 ) {\displaystyle -{\frac {\hbar ^{2}}{2m_{b}^{*}}}{\frac {\mathrm {d} ^{2}\psi (z)}{\mathrm {d} z^{2}}}+V\psi (z)=E\psi (z)\quad {\text{ for }}z>+{\frac {l_{w}}{2}}\quad \quad (3)}

Solution for above equations are well-known, only with different(modified) k and κ {\displaystyle \kappa } [16]

- - k = 2 m w E ℏ κ = 2 m b ( V − E ) ℏ ( 4 ) {\displaystyle k={\frac {\sqrt {2m_{w}E}}{\hbar }}\quad \quad \kappa ={\frac {\sqrt {2m_{b}(V-E)}}{\hbar }}\quad \quad (4)} .

At the z = + l w 2 {\displaystyle +{\frac {l_{w}}{2}}} even-parity solution can be gained from

- - A cos ⁡ ( k l w 2 ) = B exp ⁡ ( − κ l w 2 ) ( 5 ) {\displaystyle A\cos({\frac {kl_{w}}{2}})=B\exp(-{\frac {\kappa l_{w}}{2}})\quad \quad (5)} .

By taking derivative of (5) and multiplying both sides by 1 m ∗ {\displaystyle {\frac {1}{m^{*}}}}

- - − k A m w ∗ sin ⁡ ( k l w 2 ) = − κ B m b ∗ exp ⁡ ( − κ l w 2 ) ( 6 ) {\displaystyle -{\frac {kA}{m_{w}^{*}}}\sin({\frac {kl_{w}}{2}})=-{\frac {\kappa B}{m_{b}^{*}}}\exp(-{\frac {\kappa l_{w}}{2}})\quad \quad (6)} .

Dividing (6) by (5), even-parity solution function can be obtained,

- - f ( E ) = − k m w ∗ tan ⁡ ( k l w 2 ) − κ m b ∗ = 0 ( 7 ) {\displaystyle f(E)=-{\frac {k}{m_{w}^{*}}}\tan({\frac {kl_{w}}{2}})-{\frac {\kappa }{m_{b}^{*}}}=0\quad \quad (7)} .

Similarly, for odd-parity solution,

- - f ( E ) = − k m w ∗ cot ⁡ ( k l w 2 ) + κ m b ∗ = 0 ( 8 ) {\displaystyle f(E)=-{\frac {k}{m_{w}^{*}}}\cot({\frac {kl_{w}}{2}})+{\frac {\kappa }{m_{b}^{*}}}=0\quad \quad (8)} .

For [numerical solution](/source/Numerical_solution), taking derivatives of (7) and (8) gives

even parity:

- - d f d E = 1 m w ∗ d k d E tan ⁡ ( k l w 2 ) + k m w ∗ sec 2 ⁡ ( k l w 2 ) × l w 2 d k d E − 1 m b ∗ d κ d E ( 9 − 1 ) {\displaystyle {\frac {df}{dE}}={\frac {1}{m_{w}^{*}}}{\frac {dk}{dE}}\tan({\frac {kl_{w}}{2}})+{\frac {k}{m_{w}^{*}}}\sec ^{2}({\frac {kl_{w}}{2}})\times {\frac {l_{w}}{2}}{\frac {dk}{dE}}-{\frac {1}{m_{b}^{*}}}{\frac {d\kappa }{dE}}\quad \quad (9-1)}

odd parity:

- - d f d E = 1 m w ∗ d k d E cot ⁡ ( k l w 2 ) − k m w ∗ csc 2 ⁡ ( k l w 2 ) × l w 2 d k d E + 1 m b ∗ d κ d E ( 9 − 2 ) {\displaystyle {\frac {df}{dE}}={\frac {1}{m_{w}^{*}}}{\frac {dk}{dE}}\cot({\frac {kl_{w}}{2}})-{\frac {k}{m_{w}^{*}}}\csc ^{2}({\frac {kl_{w}}{2}})\times {\frac {l_{w}}{2}}{\frac {dk}{dE}}+{\frac {1}{m_{b}^{*}}}{\frac {d\kappa }{dE}}\quad \quad (9-2)}

where d k d E = 2 m w ∗ 2 E ℏ d κ d E = − 2 m b ∗ 2 V − E ℏ {\displaystyle {\frac {dk}{dE}}={\frac {\sqrt {2m_{w}^{*}}}{2{\sqrt {E}}\hbar }}\quad \quad \quad {\frac {d\kappa }{dE}}=-{\frac {\sqrt {2m_{b}^{*}}}{2{\sqrt {V-E}}\hbar }}} .

The difference in effective mass between materials results in a larger difference in [ground state](/source/Ground_state) energies.

## Nanoscale heterojunctions

Image of a nanoscale heterojunction between iron oxide (Fe3O4 — sphere) and cadmium sulfide (CdS — rod) taken with a [TEM](/source/Transmission_electron_microscopy). This staggered gap (type II) offset junction was synthesized by Hunter McDaniel and Dr. Moonsub Shim at the University of Illinois in Urbana-Champaign in 2007.

In [quantum dots](/source/Quantum_dot) the band energies are dependent on crystal size due to the [quantum size effects](/source/Quantum_size_effects). This enables band offset engineering in nanoscale heterostructures. It is possible[17] to use the same materials but change the type of junction, say from straddling (type I) to staggered (type II), by changing the size or thickness of the crystals involved. The most common nanoscale heterostructure system is [ZnS](/source/ZnS) on [CdSe](/source/CdSe) (CdSe@ZnS) which has a straddling gap (type I) offset. In this system the much larger [band gap](/source/Band_gap) ZnS [passivates](/source/Passivation_(chemistry)) the surface of the [fluorescent](/source/Fluorescent) CdSe core thereby increasing the [quantum efficiency](/source/Quantum_efficiency) of the [luminescence](/source/Luminescence). There is an added bonus of increased [thermal stability](/source/Thermal_stability) due to the stronger [bonds](/source/Chemical_bond) in the ZnS shell as suggested by its larger band gap. Since CdSe and ZnS both grow in the [zincblende](/source/Zincblende_(crystal_structure)) crystal phase and are closely lattice matched, core shell growth is preferred. In other systems or under different growth conditions it may be possible to grow [anisotropic](/source/Anisotropic) structures such as the one seen in the image on the right.

The driving force for [charge transfer](/source/Intervalence_charge_transfer) between [conduction bands](/source/Conduction_band) in these structures is the conduction band offset.[18] By decreasing the size of CdSe nanocrystals grown on [TiO2](/source/Titanium_dioxide), Robel et al.[18] found that electrons transferred faster from the higher CdSe conduction band into TiO2. In CdSe the quantum size effect is much more pronounced in the conduction band due to the smaller effective mass than in the valence band, and this is the case with most semiconductors. Consequently, engineering the conduction band offset is typically much easier with nanoscale heterojunctions. For staggered (type II) offset nanoscale heterojunctions, [photoinduced charge separation](/source/Photoinduced_charge_separation) can occur since there the lowest energy state for [holes](/source/Electron_hole) may be on one side of the junction whereas the lowest energy for electrons is on the opposite side. It has been suggested[18] that anisotropic staggered gap (type II) nanoscale heterojunctions may be used for [photocatalysis](/source/Photocatalysis), specifically for [water splitting](/source/Water_splitting) with solar energy.

## See also

- [Homojunction](/source/Homojunction), [p–n junction](/source/P%E2%80%93n_junction)—a junction involving two types of the same semiconductor.

- [Metal–semiconductor junction](/source/Metal%E2%80%93semiconductor_junction)—a junction of a metal to a semiconductor.

## References

1. ^ [***a***](#cite_ref-:0_1-0) [***b***](#cite_ref-:0_1-1) Smith, C.G (1996). "Low-dimensional quantum devices". Rep. Prog. Phys. 59 (1996) 235282, pg 244.

1. **[^](#cite_ref-GeimGrigorieva2013_2-0)** Geim, A. K.; Grigorieva, I. V. (2013). "Van der Waals heterostructures". *Nature*. **499** (7459): 419–425. [arXiv](/source/ArXiv_(identifier)):[1307.6718](https://arxiv.org/abs/1307.6718). [doi](/source/Doi_(identifier)):[10.1038/nature12385](https://doi.org/10.1038%2Fnature12385). [ISSN](/source/ISSN_(identifier)) [0028-0836](https://search.worldcat.org/issn/0028-0836). [PMID](/source/PMID_(identifier)) [23887427](https://pubmed.ncbi.nlm.nih.gov/23887427). [S2CID](/source/S2CID_(identifier)) [205234832](https://api.semanticscholar.org/CorpusID:205234832).

1. **[^](#cite_ref-3)** Leu, Sylvère; Sontag, Detlef (2020), Shah, Arvind (ed.), ["Crystalline Silicon Solar Cells: Heterojunction Cells"](http://link.springer.com/10.1007/978-3-030-46487-5_7), *Solar Cells and Modules*, vol. 301, Cham: Springer International Publishing, pp. 163–195, [doi](/source/Doi_(identifier)):[10.1007/978-3-030-46487-5_7](https://doi.org/10.1007%2F978-3-030-46487-5_7), [ISBN](/source/ISBN_(identifier)) [978-3-030-46485-1](https://en.wikipedia.org/wiki/Special:BookSources/978-3-030-46485-1), retrieved 2023-04-18{{[citation](https://en.wikipedia.org/wiki/Template:Citation)}}: CS1 maint: work parameter with ISBN ([link](https://en.wikipedia.org/wiki/Category:CS1_maint:_work_parameter_with_ISBN))

1. **[^](#cite_ref-4)** Okuda, Koji; Okamoto, Hiroaki; Hamakawa, Yoshihiro (1983). "Amorphous Si/Polycrystalline Si Stacked Solar Cell Having More Than 12% Conversion Efficiency". *Japanese Journal of Applied Physics*. **22** (9): L605–L607. [Bibcode](/source/Bibcode_(identifier)):[1983JaJAP..22L.605O](https://ui.adsabs.harvard.edu/abs/1983JaJAP..22L.605O). [doi](/source/Doi_(identifier)):[10.1143/JJAP.22.L605](https://doi.org/10.1143%2FJJAP.22.L605). [S2CID](/source/S2CID_(identifier)) [121569675](https://api.semanticscholar.org/CorpusID:121569675).

1. **[^](#cite_ref-5)** Yamamoto, Kenji; Yoshikawa, Kunta; Uzu, Hisashi; Adachi, Daisuke (2018). "High-efficiency heterojunction crystalline Si solar cells". *Japanese Journal of Applied Physics*. **57** (8S3) 08RB20. [Bibcode](/source/Bibcode_(identifier)):[2018JaJAP..57hRB20Y](https://ui.adsabs.harvard.edu/abs/2018JaJAP..57hRB20Y). [doi](/source/Doi_(identifier)):[10.7567/JJAP.57.08RB20](https://doi.org/10.7567%2FJJAP.57.08RB20). [S2CID](/source/S2CID_(identifier)) [125265042](https://api.semanticscholar.org/CorpusID:125265042).

1. **[^](#cite_ref-6)** ["HJT - Heterojunction Solar Cells"](https://www.solarpowerpanels.net.au/hjt-heterojunction-solar-cells/). *Solar Power Panels*. Retrieved 2022-03-25.

1. **[^](#cite_ref-7)** Kroemer, H. (1963). "A proposed class of hetero-junction injection lasers". *Proceedings of the IEEE*. **51** (12): 1782–1783. [doi](/source/Doi_(identifier)):[10.1109/PROC.1963.2706](https://doi.org/10.1109%2FPROC.1963.2706).

1. **[^](#cite_ref-8)** Ortiz-Quiñonez, Jose-Luis; Pal, Umapada (October 2024). ["Interface engineered metal oxide heterojunction nanostructures in photocatalytic CO2 reduction: Progress and prospects"](https://doi.org/10.1016%2Fj.ccr.2024.215967). *Coordination Chemistry Reviews*. **516** 215967. [doi](/source/Doi_(identifier)):[10.1016/j.ccr.2024.215967](https://doi.org/10.1016%2Fj.ccr.2024.215967).

1. **[^](#cite_ref-9)** Ihn, Thomas (2010). "ch. 5.1 Band engineering". [*Semiconductor Nanostructures Quantum States and Electronic Transport*](https://archive.org/details/semiconductornan00ihnt). United States of America: Oxford University Press. pp. [66](https://archive.org/details/semiconductornan00ihnt/page/n82). [ISBN](/source/ISBN_(identifier)) [978-0-19-953443-2](https://en.wikipedia.org/wiki/Special:BookSources/978-0-19-953443-2).

1. **[^](#cite_ref-10)** J. Tersoff (1984). "Theory of semiconductor heterojunctions: The role of quantum dipoles". *Physical Review B*. **30** (8): 4874–4877. [Bibcode](/source/Bibcode_(identifier)):[1984PhRvB..30.4874T](https://ui.adsabs.harvard.edu/abs/1984PhRvB..30.4874T). [doi](/source/Doi_(identifier)):[10.1103/PhysRevB.30.4874](https://doi.org/10.1103%2FPhysRevB.30.4874).

1. **[^](#cite_ref-pallab_11-0)** Pallab, Bhattacharya (1997), Semiconductor Optoelectronic Devices, Prentice Hall, [ISBN](/source/ISBN_(identifier)) [0-13-495656-7](https://en.wikipedia.org/wiki/Special:BookSources/0-13-495656-7)

1. **[^](#cite_ref-12)** Adachi, Sadao (1993-01-01). [*Properties of Aluminium Gallium Arsenide*](https://books.google.com/books?id=s7icD_5b67oC). [ISBN](/source/ISBN_(identifier)) [978-0-85296-558-0](https://en.wikipedia.org/wiki/Special:BookSources/978-0-85296-558-0).

1. ^ [***a***](#cite_ref-Debbar_13-0) [***b***](#cite_ref-Debbar_13-1) Debbar, N.; Biswas, Dipankar; Bhattacharya, Pallab (1989). "Conduction-band offsets in pseudomorphic InxGa1-xAs/Al0.2Ga0.8As quantum wells (0.07≤x≤0.18) measured by deep-level transient spectroscopy". *Physical Review B*. **40** (2): 1058–1063. [Bibcode](/source/Bibcode_(identifier)):[1989PhRvB..40.1058D](https://ui.adsabs.harvard.edu/abs/1989PhRvB..40.1058D). [doi](/source/Doi_(identifier)):[10.1103/PhysRevB.40.1058](https://doi.org/10.1103%2FPhysRevB.40.1058). [PMID](/source/PMID_(identifier)) [9991928](https://pubmed.ncbi.nlm.nih.gov/9991928).

1. **[^](#cite_ref-14)** Conley, J.; Duke, C.; Mahan, G.; Tiemann, J. (1966). "Electron Tunneling in Metal–Semiconductor Barriers". *Physical Review*. **150** (2): 466. [Bibcode](/source/Bibcode_(identifier)):[1966PhRv..150..466C](https://ui.adsabs.harvard.edu/abs/1966PhRv..150..466C). [doi](/source/Doi_(identifier)):[10.1103/PhysRev.150.466](https://doi.org/10.1103%2FPhysRev.150.466).

1. **[^](#cite_ref-15)** Bendaniel, D.; Duke, C. (1966). "Space-Charge Effects on Electron Tunneling". *Physical Review*. **152** (2): 683. [Bibcode](/source/Bibcode_(identifier)):[1966PhRv..152..683B](https://ui.adsabs.harvard.edu/abs/1966PhRv..152..683B). [doi](/source/Doi_(identifier)):[10.1103/PhysRev.152.683](https://doi.org/10.1103%2FPhysRev.152.683).

1. **[^](#cite_ref-16)** Griffiths, David J. (2004). *Introduction to Quantum Mechanics* (2nd ed.). Prentice Hall. [ISBN](/source/ISBN_(identifier)) [0-13-111892-7](https://en.wikipedia.org/wiki/Special:BookSources/0-13-111892-7)

1. **[^](#cite_ref-17)** Ivanov, Sergei A.; Piryatinski, Andrei; Nanda, Jagjit; Tretiak, Sergei; Zavadil, Kevin R.; Wallace, William O.; Werder, Don; Klimov, Victor I. (2007). "Type-II Core/Shell CdS/ZnSe Nanocrystals: Synthesis, Electronic Structures, and Spectroscopic Properties". *Journal of the American Chemical Society*. **129** (38): 11708–19. [doi](/source/Doi_(identifier)):[10.1021/ja068351m](https://doi.org/10.1021%2Fja068351m). [PMID](/source/PMID_(identifier)) [17727285](https://pubmed.ncbi.nlm.nih.gov/17727285).

1. ^ [***a***](#cite_ref-Robel_18-0) [***b***](#cite_ref-Robel_18-1) [***c***](#cite_ref-Robel_18-2) Robel, István; Kuno, Masaru; Kamat, Prashant V. (2007). "Size-Dependent Electron Injection from Excited CdSe Quantum Dots into TiO2Nanoparticles". *Journal of the American Chemical Society*. **129** (14): 4136–7. [doi](/source/Doi_(identifier)):[10.1021/ja070099a](https://doi.org/10.1021%2Fja070099a). [PMID](/source/PMID_(identifier)) [17373799](https://pubmed.ncbi.nlm.nih.gov/17373799).

## Further reading

- [Bastard, Gérald](/source/G%C3%A9rald_Bastard) (1991). *Wave Mechanics Applied to Semiconductor Heterostructures*. [Wiley-Interscience](/source/Wiley-Interscience). [ISBN](/source/ISBN_(identifier)) [978-0-470-21708-5](https://en.wikipedia.org/wiki/Special:BookSources/978-0-470-21708-5).

- Feucht, D. Lion; Milnes, A.G. (1970). *Heterojunctions and metal–semiconductor junctions*. [New York City](/source/New_York_City) and [London](/source/London): [Academic Press](/source/Academic_Press)., [ISBN](/source/ISBN_(identifier)) [0-12-498050-3](https://en.wikipedia.org/wiki/Special:BookSources/0-12-498050-3). A somewhat dated reference respect to applications, but always a good introduction to basic principles of heterojunction devices.

- R. Tsu; F. Zypman (1990). "New insights in the physics of resonant tunneling". *[Surface Science](/source/Surface_Science)*. **228** (1–3): 418. [Bibcode](/source/Bibcode_(identifier)):[1990SurSc.228..418T](https://ui.adsabs.harvard.edu/abs/1990SurSc.228..418T). [doi](/source/Doi_(identifier)):[10.1016/0039-6028(90)90341-5](https://doi.org/10.1016%2F0039-6028%2890%2990341-5).

- Kurhekar, Anil Sudhakar (2018). "Thermal annealing improves electrical properties of hetero-junction diode". *International Conference on Renewable Energy Research and Education (Rere-2018)*. AIP Conference Proceedings. Vol. 1992. p. 040027. [Bibcode](/source/Bibcode_(identifier)):[2018AIPC.1992d0027K](https://ui.adsabs.harvard.edu/abs/2018AIPC.1992d0027K). [doi](/source/Doi_(identifier)):[10.1063/1.5047992](https://doi.org/10.1063%2F1.5047992).

## External links

- Media related to [Heterojunction band diagrams](https://commons.wikimedia.org/wiki/Category:Heterojunction_band_diagrams) at Wikimedia Commons

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Adapted from the Wikipedia article [Heterojunction](https://en.wikipedia.org/wiki/Heterojunction) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Heterojunction?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.