J. R. Shealy

Highly oriented zinc oxide films grown by the oxidation of diethylzinc

Zinc oxide films, with a high degree of c‐axis orientation, have been grown on glass substrates by a chemical vapor deposition process involving the oxidation of diethylzinc. Film growth was carried out over the 200–500 °C temperature range; however, the maximum crystal orientation was found to occur with substrate temperatures between 325 and 400 °C. The effect of different substrate materials on crystallographic orientation is also described in this letter.

Coherent, monolithic two-dimensional (10×10) laser arrays using grating surface emission

Two‐dimensional, coherent AlGaAs laser arrays consisting of 100 (10×10) active elements have been fabricated using single quantum well laser structures. A surface relief grating is used both for feedback and outcoupling. The elements of the array are index‐guided ridge lasers. In one array design, the elements are coupled laterally by evanescent field overlap while in the second design, the coupling is by Y branches. Longitudinal coherence is achieved by injection coupling. The far field, emanating from a 60 μm by 5 mm aperture, measures 0.01°×1°. Both types of arrays emit more than 1 W peak power. The mode spectrum of the emitted power is contained in a ∼2–3 A wavelength interval at ∼1 W.

High‐power seven‐element grating surface emitting diode laser array with 0.012° far‐field angle

A coherent seven‐element grating surface emitting diode laser array with a predominant single‐lobe far‐field pattern having an angular divergence of 0.012° has been demonstrated. The extent of the emitting aperture was 4 mm, and the beam divergence was within 10% of the diffraction limit. Under pulsed operation the array had a peak output power of over 400 mW and a differential quantum efficiency of 15%.

Optimizing the performance of AlGaAs graded index separate confining heterostructure quantum well lasers

High efficiency AlGaAs laser structures with graded index optical confinement regions and a single GaAs quantum well active region have been prepared using organometallic vapor phase epitaxy. The optimum quantum well thickness was determined to be near 50 A where low internal losses are realized and the resulting threshold current densities were as low as 175 A/cm2 on single ended devices with a high reflectivity coating on the rear facet. The high injected carrier levels which are associated with thin quantum well structures lead to a severe degradation in device performance if the gain required to reach lasing threshold becomes too large. If the device length, the facet reflectivities, and the operating temperature were chosen to prevent the injected carrier concentrations in the quantum well from reaching a level coincident with the onset of nonradiative carrier loss mechanisms, single ended power efficiencies exceeded 55% for room‐temperature, cw operation at 840 nm.

Efficient, high-power (>150 mW) grating surface emitting lasers

Surface emitting AlGaAs second‐order distributed Bragg reflector lasers using a superlattice graded‐index separate confinement heterostructure with a single quantum well have been fabricated. The total peak power is emitted coherently from both gratings into a 0.06° full width half‐power single lobe far field pattern. Peak powers are in excess of 150 mW. The external differential quantum efficiency is as high as 30%. Under severe current modulation conditions, the stable single longitudinal mode had 20–45 dB wavelength side mode rejection.

Open tube diffusion of zinc in gallium arsenide

The diffusion of zinc in gallium arsenide has been performed under open tube conditions utilizing a zinc oxide layer as the diffusion source, silicon dioxide as an intermediate layer between the zinc oxide and the gallium arsenide, and phosphosilicate glass as a cap. The thickness of the silicon dioxide layer was used to control the amount of zinc diffused in the gallium arsenide. We have obtained a diffusion system which protects the gallium arsenide surface during the thermal cycle in a nitrogen/hydrogen flowing gas ambient. The results demonstrate the capability of reproducibly forming heavily doped p-type regions whose penetration depths were controlled from 1 to 25 µm for one to five hour-diffusions at 800°C.

Dynamically stable 0° phase mode operation of a grating-surface-emitting diode-laser array

A coherent grating-surface-emitting diode-laser array has demonstrated dynamically stable operation in the 0° phase mode. The array was operated under pulsed conditions, had a peak power output of 44 mW and a large central lobe on axis in the far field, and exhibited single-mode spectral output with better than 18-dB side-mode rejection.

High external efficiency (36%) 5‐μm mesa isolated GaAs quantum well laser by organometallic vapor phase epitaxy

High external power efficiencies of 36% are obtained from 5‐μm mesa isolated graded‐index separate‐confinement heterostructure single quantum well lasers grown by organometallic vapor phase epitaxy. Threshold currents of 21 mA are reported for a 5×96 μm cavity laser with differential quantum efficiencies of as high as 80% at 6 mW/facet. In addition, high facet power densities of 13 mW/μm are reported giving single ended output powers of 65 mW from 5‐μm uncoated facets. Even higher power densities of 20 mW/μm are observed for 1‐μm mesa stripe lasers before probe damage occurred.

The Use of Ultraviolet Radiation at the Congruent Sublimation Temperature of Indium Phosphide to Produce Enhanced InP “Schottky” Barriers

This paper describes an ultraviolet radiation-assisted process, optimized around the congruent sublimation temperature of InP, which fabricates a very thin insulating layer on InP. In developing this process, we demonstrate, among other effects, that the increase in the barrier height is not caused by the oxidation of the surface enhanced by the presence of ozone, but enhanced by a photoinduced electron transfer (PET) process. In the past, some researchers have considered similar devices to be enhanced metal-semiconductor Schottky diodes