C. J. Nuese

The effect of elastic strain on energy band gap and lattice parameter in III‐V compounds

The elastic and misfit strain in vapor‐grown InGaP/GaAs crystals was determined by measuring the lattice parameter of the InGaP before and after removal of the GaAs substrate. The energy‐band‐gap shift as a function of strain was measured in a similar manner using photoluminescence. Up to 70% of the misfit strain was found to be accommodated elastically. The critical resolved shear stress for dislocation motion was found to be ∼2×109 dyn/cm2. The rather low band‐gap shift with applied stress of ∼3×10−9 meV/dyn cm−2 was attributed to the Poisson effect. Photoluminescence was found to be a very accurate means to measure composition (and therefore lattice parameter), and empirical expressions were determined for the variation of photoluminescence wavelength with composition, lattice parameter, and energy band gap.

The temperature dependence of threshold current for double‐heterojunction lasers

The temperature dependence of the threshold current has been examined for the double‐heterojunction lasers (AlGa)As, (InGa) (AsP)/InP, and (InGaAs)/(InGa)P with emission wavelengths between 0.8 and 1.4 μm. For all lasers studied, the threshold current density was found to follow the exponential relationship Jth(T) ∝ exp(T/T0), where the constant T0 was found to be directly related to the energy‐band‐gap step, ΔEg, between the recombination region and the adjacent confining layers. The value of T0 was found experimentally to obey the relationship T0=AΔEg, with the constant A having values between 200 and 300 °K/eV for the three types of lasers studied.

Low‐threshold 1.25‐μm vapor‐grown InGaAsP cw lasers

Vapor‐grown double‐heterojunction lasers of InGaAsP/InP have been prepared with cw room‐temperature threshold currents of 85 mA and differential quantum efficiencies exceeding 50% at 1.25 μm. From several lasers, fundamentaal‐lateral‐ and fundamental‐longitudinal‐mode operation have been observed over moderate current ranges. Over 1000 h of room‐temperature cw operation has been observed to date without significant degradation.

cw room‐temperature InxGa1−xAs/InyGa1−yP 1.06‐μm lasers

Room-temperature cw laser operation at wavelengths between 1.06 and 1.12 ..mu..m has been obtained from double-heterojunction structures of In/sub x/Ga/sub 1-x/As/In/sub y/Ga/sub 1-y/P prepared by vapor-phase epitaxy. These devices have pulsed threshold current densities as low as 1000 A/cm/sup 2/ and external differential quantum efficiencies as high as 55%. Their active laser cavities are between 0.14 and 0.36 ..mu..m thick, providing fundamental transverse-mode operation with far-field patterns 50 to 60degree wide. (AIP)Room‐temperature cw laser operation at wavelengths between 1.06 and 1.12 μm has been obtained from double‐heterojunction structures of InxGa1−xAs/InyGa1−yP prepared by vapor‐phase epitaxy. These devices have pulsed threshold current densities as low as 1000 A/cm2 and external differential quantum efficiencies as high as 55%. Their active laser cavities are between 0.14 and 0.36 μm thick, providing fundamental transverse‐mode operation with far‐field patterns 50 to 60° wide.

III-V alloys for optoelectronic applications

The energy bandgap values of the 9 binary compounds, 18 ternary alloys and 15 quaternary alloys comprising the family of practical III-V materials can, in principle, provide sources, detectors, and optoelectronic components over a wavelength range between 0.51 and 7.3 μm. The material and metallurgical properties essential to the selection of III-V compounds and alloys for epitaxial opto-electronic devices are reviewed. Emphasis is given to the effects of lattice mismatch between ad joining heteroepitaxial layers, with techniques illustrated for minimizing mismatch effects in practical ternary and quaternary device structures. The most promising applications for III-V heteroepitaxial structures in the emerging fields of fiber optics, integrated optics, and photodetectors are cited.

The preparation and properties of vapor-grown In1−xGax P

In1−xGaxP has been prepared over the entire alloy system by an epitaxial vapor-phase growth technique. The energy gap dependence on alloy composition for these layers has been determined by optical absorption, Schottky-barrier photoresponse, and electroluminescence measurements. These measurements indicate a nonlinear dependence of the (direct) conduction band minimum on In1−xGaxP composition, and a direct-indirect energy gap crossover at 2.20 ev and 70 pct GaP at room temperature. Zinc-diffusedp-n junctions have been formed in the In1−xGaxP layers, and have been found to be reasonably well-behaved in regard to their I-V and C-V characteristics, and their photoresponse. The electroluminescent emission spectra contain a narrow high-energy near-bandgap peak, but are frequently dominated by low-energy impurity peaks. For indirect-bandgap alloys, impurity peaks lie approximately 0.25 and 0.5 ev less than bandgap. A third peak is found at an energy of 1.30 to 1.35 ev independent of composition, forx > 0.4.

Lifetime‐controlling recombination centers in platinum‐diffused silicon

The diffusion of Pt into Si from a silica film at temperatures between 800 and 1000 °C has been found to provide room‐temperature minority‐carrier lifetimes between 10 nsec and 1 μsec. Evaluation of the dependence of lifetime on ambient temperature and on majority‐carrier doping concentration as well as the measurement of thermally stimulated currents indicate the presence of two recombination centers: an acceptor located 0.26 eV below the conduction band edge for n‐type Si and a donor located 0.32 eV above the valence band edge for p‐type Si. The concentration of electrically active Pt centers increases exponentially with increasing diffusion temperature, and is in the range 7×1013 to 7×1014 cm−3. Minority‐carrier capture cross sections for the n‐ and p‐type Si are about 1×10−14 and 6×10−15 cm2, respectively. A simple single‐level Shockley‐Read model incorporating these centers has been used to fit observed minority‐carrier lifetime values over a wide range of temperature and to calculate the dependence ...

Comparison of Zn‐doped GaAs layers prepared by liquid‐phase and vapor‐phase techniques, including diffusion lengths and photoluminescence

p‐type Zn‐doped GaAs layers have been prepared by both liquid‐phase (LPE) and vapor‐phase (VPE) epitaxial growth techniques. Both techniques allow controlled Zn doping between ∼9×1017 and 3×1019 cm−3. For the LPE technique, the hole concentration (p) is related to the concentration (XZn) in the Ga solution by p=5×1020(XZn)1/2. The surfaces of the LPE layers have a characteristic ripple, in contrast to the optically flat surfaces representative of vapor‐grown layers. Minority‐carrier (electron) diffusion lengths in the LPE layers decrease from 10 to 5 μm with increasing hole concentrations between 9×1017 and 3×1019 cm−3. Diffusion lengths for comparably doped VPE layers are about two times smaller. The room‐temperature photoluminescence characteristics of both types of layers have similar dependences on hole concentration, which can be used as a calibration for nondestructive hole concentration determination. Peak photoluminescence intensities of the two types of layers occur at ∼1×1019 cm−3, and are appro...

Reduced degradation in InxGa1−xAs electroluminescent diodes

Lifetests at 1000 A/cm2 have been carried out on InxGa1−xAs (0<x<0.25) electroluminescent diodes prepared by vapor‐phase and liquid‐phase epitaxy. As the InAs content of the alloys is increased from 0 to 25 mole%, the junction emission energy shifts from 1.4 to 1.05 eV and the degradation rate decreases by about three orders of magnitude. Consequently, diodes emitting near 1.06 μm at room temperature show little or no degradation after 1000 h at 1000 A/cm2 bias. In addition, lifetest results for a few vapor‐grown GaAs1−xPx and InxGa1−xP electroluminescent diodes are consistent with the strong exponential dependence of degradation rate on emission energy observed for the InxGa1−xAs diodes. This effect has been found to be independent of large differences in growth technique, dislocation density, and initial electroluminescence efficiency. Moreover, p‐n junctions of InxGa1−xAs have been found to be relatively insensitive to fabrication and device‐mounting procedures that are known to be deleterious to simil...

Luminescence from In0.5Ga0.5P prepared by vapor‐phase epitaxy

The photoluminescence from n‐ and p‐type In1−xGaxP with x≃0.5, prepared by vapor‐phase epitaxy on GaAs substrates, has been studied between 4.2 and 300 K. This material is of particular practical interest because of its close lattice‐parameter match with GaAs and direct energy band gap of 1.9 eV. At very low temperatures, four major emission bands have been identified, involving intrinsic recombination, donor—to—valence‐band transitions, conduction‐band—to—acceptor transitions, and donor‐acceptor transitions. The intrinsic recombination dominates in all the samples above about 150 K. The spectra are consistent with a shallow donor ionization energy of 7±1 meV, the same value as in InP. The spectral data of Cd‐doped samples (with p varying from 1.8×1016 to 9.3×1017 cm−3) suggest a consistent shift of the Cd acceptor ionization energy to lower values with increasing doping. The extrapolated value for very low doping is 59±2 meV at 50 K. The residual donor density is low in all the p‐type samples studied (≲ ...