Gregory H. Olsen

Calculated stresses in multilayered heteroepitaxial structures

A useful closed‐form expression for stresses within individual layers of a multilayer composite has been obtained as a function of position within the layer. Equal and isotropic elastic constants were assumed in the calculation, although the error introduced by this assumption is found to vary by no more than the difference in elastic constants. Unequal elastic constants may be handled via computer solutions. The stresses within heterojunction AlxGa1−xAs/GaAs lasers are calculated as an example of the technique. The addition of Al to the active GaAs region is shown to have a drastic effect upon the active‐region stress, changing it from tension to compression. This change of sign in stress is correlated with improvements in operating lifetimes of lasers.

A planar InP/InGaAs avalanche photodiode with floating guard ring and double diffused junction

The authors discuss the fabrication, performance, and design of a novel, planar In/sub 0.53/Ga/sub 0.47/ As/InP separate absorption and multiplication region avalanche photodiode (SAM-APD) with floating guard rings and a double Zn diffused junction. The APD, grown by both vapor phase epitaxy and metalorganic vapor phase epitaxy, is observed to have a uniform gain of 85, a minimum primary dark current density of 5*10/sup -6/ A/cm/sup 2/ at 90% of breakdown, and a capacitance of 0.4 pF for a front-side illuminated device. Both experimental and analytical results show that the double-diffused floating guard ring structure prevents edge breakdown, and also greatly reduces the electric field along the semiconductor/insulator surface. The operation mechanisms and the optimum design of the planar APD based on a two-dimensional device model are discussed. >

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.

Above-room-temperature optically pumped midinfrared W lasers

We report temperature-dependent pulsed lasing performance, internal losses, and Auger coefficients for optically pumped type-II W lasers with wavelengths in the range of 3.08–4.03 μm at room temperature. All lased to at least 360 K, and produced 1.5–5 W peak power at 300 K. Internal losses at 100 K were as low as 10 cm−1, but increased to 90–360 cm−1 at 300 K. Room temperature Auger coefficients varied from 5×10−28 cm6/s at the shortest wavelength to 3×10−27 cm6/s at the longest.

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.

Reduction of dislocation densities in heteroepitaxial III−V VPE semiconductors

Electron microscope evidence from {011} cross−sectional samples of InxGa1−xP/GaP is presented to demonstrate the reduction of dislocation densities in constant composition regions of {100} III−V samples prepared by vapor−phase epitaxy with compositional grading having over−all misfit strains as high as 3.7%. Dislocations are shown to be confined to the graded region by an abrupt compositional step in both step− and continuous−graded samples. The crystal growth technique described works well for epitaxial layers which are in compression but not for those which are in tension.

The effect of gas‐phase stoichiometry on deep levels in vapor‐grown GaAs

A deep (0.82 eV) impurity level has been observed via transient capacitance measurements in GaAs prepared under various gas‐phase stoichiometries. The density of these impurities increased with increasing AsH3/GaCl ratio in the vapor phase ranging from 2×1013 cm−3 for a 1/3 ratio to 9×1013 cm−3 for a 3/1 ratio. The minority‐carrier lifetime in these same samples decreased from 15 to 5 nsec with increasing AsH3/GaCl ratio. These deep levels, which serve as recombination centers for lifetime reduction, appear to originate from point defects introduced by deviations from stoichiometry toward the As‐rich side.

Universal stain/etchant for interfaces in III‐V compounds

The application of the A‐B dislocation etch to the delineation of interfaces in III‐V compounds is described. The etchant is easy to use and has worked on all III‐V compounds tested to date.

InGaAsP quaternary alloys: Composition, refractive index and lattice mismatch

Extrapolation schemes for the calculation of InGaAsP material parameters are described. Experimental data on alloy composition, bandgap, lattice parameter and refractive index are presented and compared with calculated values. Refractive index steps between InGaAsP and InP were found to vary significantly with lattice mismatch. Errors in alloy composition of mismatched epitaxial layers, deduced from bandgap and lattice parameter measurements, can be caused by a tetragonal distortion of the crystal lattice.

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.