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The potential barrier heights, thickness, and capacitance of abrupt heterojunction space-charge regions under forward voltages are treated analytically, and a model for this is developed. Physical effects such as free-carrier charges and interface states in the heterojunction space-charge region are considered. Comparison of the present model and other models for a Gaas/Si heterojunction diode is included. Experimental aspects regarding the heterojunction capacitance are also briefly discussed. Die Potentialbarrierenhohen, die Dicke und die Kapazitat des Raumladungsgebiets eines abrupten Heteroubergangs werden analytisch behandelt und es wird ein Modell hierfur aufgestellt. Es werden physikalische Effekte wie die Ladungen freier Trager und Grenzflachenzustande in dem Raum-ladungsgebiet behandelt. Es wird ein Vergleich zwischen dem vorgestellten Modell und anderen Modellen fur eine Gaas/Si-Heteroubergangsdiode durchgefuhrt. Gleichfalls werden experimentelle Ergebnisse zur Kapazitat des Heteroubergangs kurz diskutiert.

A determination has been made of the effective interfacial recombination at Al0.25Ga0.75As/GaAs and Al0.5Ga0.5As/GaAs heterojunctions. The recombination velocity was deduced from the dependence of the minority‐carrier lifetime on junction spacing in heterojunction diodes. For heterojunction spacings in excess of about 1 μm, the interfacial recombination can be characterized by a recombination velocity of 4×103 and 8×103 cm/s for Al0.25Ga0.75As/GaAs and Al0.5Ga0.5As/GaAs heterojunctions, respectively. However, for double‐heterojunction spacings below 1 μm, the minority‐carrier lifetime is invariant, suggesting that the interfacial recombination velocity decreases with decreasing heterojunction spacing. No such effect is observed in single‐heterojunction diodes.

The light-beam-induced current (LBIC) of an InGaAsP/GaAs heterojunction diode is studied in order to obtain a qualitative characterisation of the in-depth profile of the defect distribution. A region containing defects is assumed to be the short-lifetime region, and the LBIC of the heterojunction diode is calculated by solving the diffusion equations. It is shown that, by measuring the photocurrent J( lambda ), the in-depth profile of the diffusion length distribution can be determined. The LBIC of an InGaAsP/GaAs diode fabricated by LPE is measured and compared with the intensity profile of the photoluminescence. Both profiles represent the same defects distribution; this demonstrates the usefulness of the present method.

Mesa‐isolated, p+nn+, GaAs/Al0.30Ga0.70 As/GaAs, double heterojunction diodes are reported which have excellent electrical characteristics over the full temperature range from 23 to 400 °C. These devices have diode law ideality factors of approximately 1.1 at any temperature for forward current densities greater than 10−3 A/cm2 and have reverse leakage current densities of 4×10−10 A/cm2 at 23 °C and 2×10−2 A/cm2 at 400 °C. AlxGa1−x As is used only in critical device regions to ensure that GaAs heterojunction contacts are made to the wider band‐gap materials and to allow the chemically reactive AlxGa1−x As to be encapsulated by GaAs. These results demonstrate that the GaAs/AlxGa1−x As chemical system is a good materials candidate in which to base a technology for electronic components operated at high temperatures.

A possible structure for increased single junction photovoltaic efficiency is a heterojunction diode with bandgaps differing by a factor of two or more. Excess energy from carriers photogenerated in the wide bandgap material may excite additional carriers in the narrow bandgap material by impact ionization. Photovoltaic efficiencies are calculated as a function of bandgap for both ideal and good quality solar cells. Assuming a plausible solar spectrum, the maximum efficiency may be increased by impact ionization, but the potential gain is relatively modest. Ideal cell maximum efficiency can be increased 1.5%; with more realistic assumptions, the increase is less than 1%.

We have studied the effect of compositional grading on the characteristics of N AlGaAs p GaAs heterojunction diodes, and have found that the elimination by grading of the heterojunction spike leads to a factor of 10 difference in the magnitude of current density. The behavior of heterojunction diodes has also been compared to GaAs homojunction diodes. Ideality factors for graded diodes were as good as n = 1.12, while those for the abrupt diodes were n = 1.25−1.30. At low forward-bias voltages the I–V characteristics are dominated by a recombination mechanism which leads to a temperature-independent logarithmic slope with applied bias. We also observe a difference in the built-in voltage between the graded-, abrupt- and homojunction diodes. By comparing the built-in voltage between abrupt heterojunction diodes and homojunction diodes, a value of ΔE c = 0.64 ΔE G for the conduction-band-edge discontinuity was obtained in excellent agreement with recent measurements on other device structures. An understanding of the current conduction mechanisms of these pN heterojunction diodes is essential for the understanding of GaAs/AlGaAs heterojunction bipolar transistors.

The effect of carrier recombination in the depletion region on the I-U characteristics of a hetero-junction diode is considered. It is found, that recombination currents affect the I-U characteristics of symmetrically doped heterojunction diodes with large energy band offsets for the majority carrier type in the large gap material differently than heterojunction diodes with a large band offset for the majority carrier type in the small gap material. The two cases are illustrated with numerical calculations for p-GaAs on n-AIAs and n-GaAs on p-AIAs. Es wird der Einflus der Ladungstragerrekombination in der Verarmungsrandschicht auf die I-U-Charakteristiken einer Heterojunction-Diode betrachtet. Es wird gefunden, das die Rekombinationsstrome die I-U-Charakteristiken von symmetrisch dotierten Heterojunction-Dioden mit grosen Energiebandabweichungen fur die Majoritatsladungstrager in Materialien mit grosem Bandabstand anders als in Heterojunction-Dioden mit grosen Energiebandabweichungen fur die Majoritatsladungstrager in Materialien mit geringem Bandabstand beeinflussen. Die beiden Falle werden mit numerischen Berechnungen fur p-GaAs auf n-AlAs und n-GaAs auf p-AlAs illustriert.

A theory of transient SCLC for saw-tooth voltage pulses has been developed on the basis of M any and R acavy 's method. Expressions have been obtained which allow the determination of some parameters of the material, particularly the effective mobility of carriers using special points of the transient characteristics. Experimental investigation of the transient characteristics of thin-film InCdSSiO x Al heterojunction diodes have been carried out to verify the theory developed for the saw-tooth voltage pulse. The I–V characteristics observed with the help of a curve-tracer at sufficiently fast linear voltage increase exhibit a region of n -type negative differential resistance. The theory is found to be in satisfactory agreement with the experiment in the regions where the solutions are derived in analytical form.

CdTe layer formation at CdS-Te interface during fabrication of thin film, Au-CdS-Te heterojunction diodes by vapor deposition

ZnSe-Si and ZnSe-GaAs n-p heterojunctions are produced by rf-sputtering of ZnSe onto single crystal wafers of Si and GaAs at 200°C. These sputtered diodes contain high resistivity ZnSe layers, and the SCLC is predominant in the forward current-voltage characteristics. Annealing the diodes in Zn vapour at 700°C for 1 hr results in the decrease of the SCLC, and the thermal emission current in series with tunneling current becomes predominant. A bias-temperature treatment of the sputtered diodes at 155°C in a forward bias condition is found to enhance their photovoltaic effects.

ZnTe-InAs heterojunctions are prepared by the liquid-phase epitaxial growth technique. InAs layers are grown from the In solutions on ZnTe substrates. The study on the optical transmittance reveals that InAs-ZnTe mixed-crystal layer exists at the boundary. The ZnTe-InAs heterojunction diodes show SCLC characteristics at forward bias. It is suggested that in the ZnTe substrates, high-resistivity layers are formed by the diffusion of In from the InAs layers. The forward I–V characteristics can be explained by the hole space-charge limited flow in the high-resistivity layers. By using Lampert theory, it is concluded that this layer has a trap density of about 1×1014cm-3 and the trap level is located about 0.38 eV above the valence band edge.

A significantly high non‐Ohmic forward voltage has been observed in n‐GaAs/p‐Ge and p‐GaAs/n‐Ge injection heterojunction diodes which have hard reverse electrical characteristics and whose wide‐gap emitters were of relatively low doping levels. Theory and experiment are compared and conditions for enhancing this phenomenon are stated. An SEM micrograph of the grown Ge epitaxial layer is included and growth conditions are described.

The resistance to gradual degradation of (AlGa)As−GaAs heterojunction structures prepared by liquid phase epitaxy is shown to be greatly improved by using a very fast cooling rate. The specific diodes described are of interest as high−speed (200 MHz) LED sources for fiber−optic communications. It is suggested that the improved degradation resistance results from a reduction in the arsenic vacancy concentration incorporated in the GaAs grown at the high cooling rates.

The current‐voltage characteristics of p‐Ge/n‐CdS heterojunction diodes have been studied for a wide range of diodes fabricated under different CdS film growth conditions. It has been found that under certain growth conditions the diodes possess two resistance states: Switching from the high‐ to low‐resistance state occurs with a small reverse‐bias voltage, while switching from the low‐ to high‐resistance state occurs with a small forward‐bias voltage. Measurements have been carried out on the junction capacitance, and it has been found that the capacitance increases when the diode is switched to the low‐resistance state and reverts to its initial value when the diode is switched back to the high‐resistance state. It is concluded that the two resistance states of the diode are associated with a junction phenomenon and not with some change in the physical state of the n‐type film. A prerequisite for this behavior would appear to be that the dielectric relaxation time should be greater than the diffusion li...

Electrical characterization of ZnSe/GaAs n-p heterodiodes grown by molecular beam epitaxy under different Zn/Se flux ratios is reported. Large tunability of the band discontinuity at the heterojunction is shown by photocurrent measurements at low temperature with conduction-band offsets in the range 0.26-0.75 eV. Achievement of device-grade heterostructures with engineered offsets is shown under appropriate growth conditions.

The conduction mechanisms governing the dark current-voltage characteristics of a-SiC:H/a-Si:H/c-Si pin heterojunction diodes are determined by the use of an electrical model. In particular, the influence of the a-SiC:H thickness layer on the conduction mechanisms is studied. For a 5 nm thick a-SiC:H layer, the conduction mechanisms of the heterojunction diode are the same than a homojunction Silicon diode.

Using a new device concept, a unique semiconductor strain sensor has been demonstrated in the laboratory. It is a p-n heterojunction diode which is fabricated by vacuum evaporation techniques directly onto flexible substrate. This sensor's mechanical input properties are controlled by the choice of substrate, and it has a low-impedance voltage source output characteristic.

We report the nearly ideal electrical characteristics of p-Ge/N-GaAs heterojunction diodes grown by molecular beam epitaxy. The temperature and device size dependencies of the current-voltage characteristics have been investigated. At room temperature, unity ideality factor has been demonstrated over almost six decades of current.

We report the first internal photoemission studies of GaInAs and AlInAs Schottky diodes in the infrared region. The photoresponses exhibit very high external quantum yield (about 1.22%) and high speed response (rise time smaller than 115 ps). Internal photoemission response has also been observed for the first time for a GaInAs/AlInAs heterojunction diode, due to the conduction band discontinuity at the interface. An internal barrier height of 0.4 eV was obtained.

Different growth behaviour of the Cu x S layer was obtained experimentally when the Cu x S layer was grown chemically on the basal plane of the CdS. The growth process of the layer is discussed by assuming the different diffusion velocities of Cd element in the Cu x S and Cu2S. The electric properties of the non-heat treated single crystal Cu2S–CdS heterojunction diode are also discussec with respect to the variation of the constituent elements in the transition region of the heterojunction diode.

The current-voltage characteristics and visible and X-ray photocurrent characteristics have been investigated for a heterojunction diode constructed of plasma-deposited hydrogenated amorphous silicon (a-Si:H) and single crystal cadmium telluride (c-CdTe). Devices showed low reverse bias saturation current, a photoresponse spectrum ranging from approximately 400-800 nm and a 3 decade increase in reverse bias saturation current when exposed to 40 keV X-rays.

A heterojunction of n·Ga x Al1-x Sb–p·GaSb was prepared by vapor-phase deposition in a conventional closed-tube system with iodine as a transport agent. Electrical and photoelectrical characterization was carried out on the heterojunction diodes. The I-V characteristics showed that η in the forward current varied between 1 and 2 in the experimental range 206–300 K. The C-V measurements indicated that the heterojunction was an abrupt one with a diffusion potential of 0.65 V. The spectral photovoltaic response gave a broad peak between 1.35 and 1.55 µm.