Deep hole traps in VPE p-type InP

Deep hole traps were investigated in vapour phase epitaxial p-type InP by transient capacitance spectroscopy. A total of five hole traps were observed with activation energies of 0.09, 0.22, 0.29, 0.41 and 0.50 eV in Al-InP Schottky barriers and p-n+ junctions. Trap concentrations ranged from 1013 to 1014 cm?3.     

VPE growth of high purity and high uniformity InGaAs/InP epilayers on InP

PIN and avalanche photodiodes are vital component parts of today's optical communication systems. For these, InP/InGaAs/InP heteroepitaxial structures are required. To improved the quality and yield of these devices, the epitaxial wafers must be of very high purity and uniformity. At Sumitomo Electric we have grown the above mentioned epitaxial layers by the chloride VPE method, which is safe and has a usefully high growth rate. This article describes the growth technique and the characterization of high uniformity and high purity InGaAs/InP epilayers.     

Selective growth of InP in the low pressure hydride VPE system

We have investigated the selective growth of InP in a low pressure hydride VPE system. Although the system operates further from thermodynamical equilibrium than the atmospheric pressure VPE system, high selectivity is found in a wide temperature range. The effects of the deposition temperature, the orientation and the geometric dimensions of the selectively grown structures on the growth behaviour are investigated. Additional experiments using unpatterned substrates of different surface orientations are performed to explain the formation of the typical shape of the structures. The results indicate that reaction kinetics mainly control the selective growth at low and medium growth temperatures. Only at high temperatures can effects of mass transfer be found. As a consequence, a comparable weak dependence of the growth rate on the width of selectively grown structures is found.     

Residual donors and acceptors in high-purity GaAs and InP grown by hydride VPE

Residual donors and acceptors in epitaxial films of GaAs and InP grown by the hydride vapor phase epitaxy technique were investigated using the complementary techniques of photothermal ionization spectroscopy and variabletemperature photoluminescence. High-purity samples of GaAs grown in three different laboratories were compared and high-purity InP samples were also measured. The dominant shallow acceptors in the GaAs samples were found to be C and Zn, and deep Cu and Mn acceptors were also observed. The donors Si, S, and Ge were observed in the GaAs with S being dominant. A clear correlation was observed between the gas phase stoichiometry during growth and the relative incorporation of column IV donors (Si and Ge) and column VI donors (S) in GaAs. Substrate quality, source purity, and atmospheric contamination of the growth system were found to influence the photoluminescence spectra of the GaAs samples. In the InP samples three shallow acceptors were observed including Zn, an unknown shallow acceptor level with E_A ≃ 21 meV, and an acceptor which may be either C or Mg. An unusual deep, structured emission band was also seen. The donors in the hydride InP were also found to be present in LPE InP and are believed to be Si and S.     

Orientation dependentp-type conversion of Fe:InP in hydride VPE regrown EMBH lasers

We have studied semi-insulating Fe:InP regrowth of etched mesa buried heterostruc-ture lasers by hydride vapor phase epitaxy. Type-sensitive staining and electron beam induced current photographs have shown that regions near the original etched mesa are p-type instead of semi-insulating in a number of our wafers. These regions begin and end on distinct crystal boundaries, indicating that thep-type conversion is not due to simple diffusion of Zn out of the laser base structure, but is associated with uncontrolled growth of {111}_In crystal planes.     

An investigation on hydride VPE growth and properties of semi-insulating InP:Fe

Growth of highly resistive semi-insulating InP : Fe has been achieved by the Hydride VPE technique in an ambient consisting mostly of nitrogen. After dealing with some thermodynamic considerations pertinent to InP:Fe growth, the experimental growth parameters are described. It is shown that various amounts of iron can be introduced into the InP crystal just by varying the temperature of the iron source. The crystal quality of the grown material is estimated to be good by etch pit density and x-ray diffraction analyses. Current-voltage behaviour and capacitance studies on ann ⁺-SI-n ⁺ structure are explained by invoking the theory of current injection in solids by Lampert and Mark: the experimental current densities at the threshold of each observed regime are compared with the theoretically derived current densities; in the absence of current injection, the measured capacitance is found to be the same as the geometrical capacitance.     

汽相外延ZnSe单晶的激光发射(英文)

Much work has been done on the laser emission from ZnSe under electron beam pumping. In this paper, the stimulated emission from ZnSe epilayer has been investigated under a nitrogen laser excitation. The ZnSe epilayers were grown by vapor phase epitaxy on (100) GaAs substrates. Optically pumped lasers were fabricated from the ZnSe epilayers by cleaving the ZnSe/GaAs along the (100) cleavage planes into rectangles with widths 100-600μm, and found to operate in the blue portion of the visible spectrum at 77K. The threshold of laser emission was determined to be about 1MW/cm2 from the dependence of the total light output on excitation intensity. The exciton-exciton inelastic collision process is the dominant laser emission mechanism in the ZnSe laser at 77K.     

Temperature dependence of Si-GaAs energy gap using photoconductivity spectra

In the present work, we study the Energy gap (E_g) of the Si-GaAs at various temperatures in the range from 250 up to 350 K, using the photoconductivity method, in order to find the relation between the E_g and the temperature. We have measured the photocurrent as a function of photon energy from 1.36 up to 1.55 eV for each temperature. From the analysis of the spectra for each temperature we have found three peaks corresponding to inter-band transitions and we plotted the energy that corresponds to the peaks as a function of temperature.     

Excitonic effects in the photoconductivity of quantum-well GaxIn1−x As/InP structures

The photoconductivity spectra of quantum-well structures consisting of 50 alternating 7 to 12-mm-thick Ga_xIn_1−x As (x=0.47) layers forming quantum wells and 10 to 15-nm-thick InP barriers have been investigated. Characteristic excitonic peaks 11H, 11L, 13H, 22H, and 22L were observed in the high-quality structures. A strong temperature dependence was found for the 11H exciton, while no such dependence was observed for any of the other excitons. This is explained by the fact that the 11H state of an exciton falls in the range of energies which are forbidden for free carriers, while the remaining states are resonance states and overlap with the continuous spectrum. The thermal activation energy of photoconductivity was found to be 150±30 meV, much greater than the exciton binding energy and close to the depth of the potential well for electrons. This shows that the photosensitivity is due to above-barrier charge-carrier transfer and that the tunneling transfer between the wells is negligible. Fiz. Tekh. Poluprovodn. 31, 848–850 (July 1997)     

Orientation dependent growth behaviour during hydride VPE regrowth of InP:Fe around reactive ion etched mesas

An investigation on the hydride vapour phase epitaxy (HVPE) growth of SI-InP : Fe on patterned surfaces indicates that iron incorporation does not always synchronize with the rate of growth. This is especially true in certain crystallographic directions,e.g., (1,− 1,0) where the growth rate is high. This phenomenon has been attributed to the local chemistry which limits the availability of iron or to a simple kinetically limited supply of iron when the growth rate is high. However, it is shown that by a two step procedure such a synchronization can be achieved. The proposed procedure which is applicable to reactive ion etched vertical mesas is tested on a laser mesa and the surrounding SIInP:Fe is found to provide good current confinement and high modulation performance.     

Specific features of intrinsic photoconductivity spectra of copper-compensated indium phosphide

The intrinsic photoconductivity of copper-compensated indium phosphide has been studied. It is found that mechanical polishing of a sample surface gives rise to an additional photoconductivity peak in the region of the fundamental absorption edge. This peak disappears upon storage of the sample. The dependence of the shape of the photoconductivity spectrum on the storage time, electric-field strength, and position of the light spot with respect to the contacts was determined. The results are explained in terms of variation in the lifetime of nonequilibrium carriers across the sample thickness. An expression qualitatively describing the photoconductivity spectra is presented.     

Effect of surface scattering of carriers in the photoconductivity spectra of CdS

The effect caused by electron scattering at a semiconductor surface is revealed in the low-temperature (77 K) photoconductivity spectra of second-group CdS crystals subjected to the influence of an external enriching transverse electric field.     

Gain spectra in GaInAsP/InP proton-bombarded stripe-geometry DH lasers

We have measured gain spectra for TE polarization in a GaInAsP/InP laser as a function of dc bias current below laser threshold. The measurements were made on a low-threshold device with a stripe geometry defined by proton bombardment. A number of other characteristics of this and similar devices from the same wafer are also reported. These data permit the maximum gain coefficient of the active layer gmaxto be evaluated as a function of nominal current density Jnom. We obtain the linear relationshipg_{max} = (3.1 times 10^{-2}/eta_{r})(J_{nom} - eta_{r} 5.4 times 10^{3}), where ηris the radiative quantum efficiency. Our data apply only for large gain (g gsim 150cm^-1) and large Jnombecause the active layer of the test device is thin (0.1 μm).     

Excitonic structure formation in the photoconductivity spectra of CdS crystals at modulated excitation

The low-temperature (77 K) photoconductivity spectra of CdS crystals are studied at different frequencies of photoexcitation modulation. The effect of transformation of the photoconductivity spectrum from type I to type II is observed, as modulated photoconductivity excitation is used instead of unmodulated excitation. A model of the fine (excitonic) structure formation in the spectra of the modulated photoconductivity excitation for the semiconductor is proposed.     

Optical gain spectra of InGaAsP/InP double heterostructures

We report the first optical gain measurements on InGaAsP/ InP double heterostructures with composition corresponding to an emission wavelength of about 1.3 μm at 300 K. At optical pumping levels of about 1 MW/cm²the maximum gain values of the best samples available are 800 cm^-1at 2 K, 500 cm^-1at 77 K, and 200 cm^-1at 300 K. We conclude from low-intensity luminescence and absorption spectra, that the laser transition corresponds to free-carrier recombination between band-tail states, which are present even in not intentionally doped material. Although these tail states result in rather broad low-intensity luminescence, narrow gain spectra comparable to those of GaAs/GaAlAs double heterostructures are obtained.     

Semi-insulating InP: Fe regrowth by the hydride VPE technique aroundp-InP substrate laser mesas fabricated by reactive ion etching

Successful regrowth of semi-insulating (SI) InP: Fe by the hydride vapour phase epitaxy technique around reactive ion etched vertical mesas of laser grown on Zn dopedp-InP substrate is demonstrated. The device performance of the buried heterostructure laser is presented. The current confining property of the regrown SI-InP: Fe are good although it lies adjacent to InP: Zn.     

Properties of Zn-doped P-type In0.53Ga0.47as grown by vapor phase epitaxy (VPE) on InP substrates

Electrical properties of Zn-doped, p-type In_0.53Ga_0.47As grown by the vapor phase epitaxy (VPE) technique are presented. High (p ∼ 4.0 × 10¹⁹ cm⁻³) p-type doping and low resistivity (ρ ∼ 2.8 × 10⁻³ Ωsu−cm) was obtained. These propertie's are useful in the formation of ohmic contacts in laser diodes and photodiodes fabricated from the quaternary and ternary alloy systems. A calibration curve for the non-destructive determination of carrier concentration from photoluminescence linewidths has been obtained.     

Specific features of photoconductivity spectra of the CdTe/CdHgTe epitaxial graded-gap heterostructures

Based on studies the structural and photoelectric properties of CdTe/CdHgTe graded-gap heterostructures, it is found that the metallurgical interface between the materials, which is located in the structure bulk, is enriched with structural defects. An increased recombination rate is characteristic of this interface. This circumstance is the cause of the loss of photosensitivity in the mid-IR range of the broadband photoconductivity spectra of these heterostructures. For the epitaxial layers thinner than 10–20 μm, the effect of the metallurgical interface can manifest itself in the reduction or complete loss of photosensitivity.     

Effect of nonstoichiometry and doping on the photoconductivity spectra of GeSe layered crystals

The polarization photoconductivity spectra of Bi-doped nonstoichiometric GeSe layered crystals grown by static sublimation were investigated. Two strongly polarized maxima at the photon energies hν_max = 1.35 eV (E ∥ a) and 1.44 eV (E∥ b) due to the V ₁ ^V → V ₁ ^c and Δ ₂ ^v → Δ ₁ ^c optical transitions, respectively, were found in the spectra of nominally undoped GeSe crystals near the intrinsic absorption edge at 293 K. In the low-temperature region, an exciton photoconductivity band peaked at hν_max=1.32 eV, which is due to exciton dissociation at the cation vacancies, was revealed. With an increase in excess Se in crystals, a sharp increase in the intensity of the exciton peak in the photoconductivity spectra was observed. It is shown that doping of GeSe crystals with donor Bi impurity is an effective tool of the control of their electrical and photoelectric properties. Although introduction of Bi into germanium monoselenide does not lead to the conductivity conversion from the p to n type, a sharp increase in the resistivity is observed, the crystals become photosensitive, and a strong impurity band peaked at 1.11 eV arises in the photoconductivity spectra.