Michael Ettenberg

Minority carrier diffusion length and recombination lifetime in GaAs:Ge prepared by liquid‐phase epitaxy

The electron diffusion length in p‐type GaAs:Ge grown by liquid‐phase epitaxy has been measured as a function of hole concentration. The direct measurements were made by two different techniques —a laser beam scan on beveled samples and an α particle scan on cleaved samples. These measurements are in good agreement and show that the diffusion length increases from ∼6 μm at p=1×1019 cm−3 to ∼20 μm at p=7×1016 cm−3. In addition, the diffusion length was estimated from electroluminescent decay times of p‐n junctions and the values obtained were in reasonable agreement with those directly measured for the same materials.

A new dielectric facet reflector for semiconductor lasers

Described in this letter is a new dielectric reflector designed for injection laser facets which consists of alternating quarter‐wavelength layers of Al2O3 and Si. The reflectivity for six layers can be made ≳0.98 over a wavelength range from ∼0.7 to ≳2 μm. By choosing the appropriate number of quarter‐wavelength layers and the final layer thickness the reflectivity can be varied between 0.01 and 0.98. Finally, both Si and Al2O3 are impervious to the chemical cleaning and wetting agents and solders used during the mounting of (AlGa)As cw injection lasers.

Mass spectrometric and thermodynamic studies of vapor-phase growth of In(1−x)GaxP

Abstract A time-of-flight mass spectrometer was coupled directly to an open tube vapor growth system. The vapor composition and the processes occurring during the deposition of In (1−x) Ga x P alloys were studied. It was found that the vapor species present in this system are InCl, GaCl, HCl, PH 3 , P 2 , P 4 and H 2 . The deviations from the chemical equilibrium in the system were determined and measured. A chemical equilibrium model was set and used to calculate the equilibrium partial pressures of all species under a wide range of experimental conditions. These calculations were used to predict successfully the proper conditions for growth of desired In (1−x) Ga x P alloys.

Very high radiance edge-emitting LED

In this paper we describe a new light-emitting diode (LED) whose radiance is 1000 W/cm2sr, an order of magnitude higher than any previous LED. The LED is an (AlGa)As double-heterojunction edge-emitting structure. This structure acts as a waveguide for the internally generated light, and with appropriate Al concentration difference at the heterojunctions ( \Deltax \approx 0.3 ) and active region width (∼500A), the radiation pattern perpendicular to the junction can be less than 30° (FWHM). For fiber-optic communications this LED is capable of coupling 850 μw, at a coupling loss of only -10 dB into a 0.14-numerical-aperture (NA), 90-μm-diam low-loss fiber. The LED is capable of being directly modulated at 250 MHz and has a spectral width of less than 300 A.

Degradation of AlxGa1−xAs heterojunction electroluminescent devices

Experimental results are presented correlating the operating life of (AlGa)As heterojunction diodes with recombination region doping and Al concentration. For a given doping level, the operating life is shown to increase with the addition of Al. The relationship between spontaneous emission degradation and lasing properties has also been studied.

Electroluminescence and photoluminescence of GaAs : Ge prepared by liquid phase epitaxy

Optical data are presented relating the photoluminescence emission of GaAs : Ge epitaxial layers with hole concentrations in the range from 6 × 1016 to 2.7 × 1019 cm−3. These data are supplemented with electroluminescence results obtained using diodes where the p side of the junction consists of GaAs : Ge. Measurements reported include the peak position of the electroluminescence and photoluminescence peaks, half‐intensity bandwidths, and radiative efficiency at room temperature.

Beamwidth approximations for the fundamental mode in symmetric double-heterojunction lasers

The beamwidth for the fundamental TE 0 mode in symmetric DH lasers is approximated within 4 percent by analytical formulas covering wide ranges of cavity thickness and refractive index steps. By using a Gaussian approximation for near-field distributions, and numerically calculated beamwidth curves, we find a Gaussian beam-like expression for the beamwidth, over the range 1.5 , where D is the normalized guide thickness. In the nonGaussian region 0 , the beamwidth is estimated by using a corrected Dumke-like asymptotic approximation.

Radiation trapping in laser diodes

This paper is concerned with the problem of cavity geometries which exhibit anomalously low radiative efficiencies. While the ideas presented apply to any type of cavity, the experiments and discussion refer specifically to the type of cavity of importance in commercial injection lasers, a Fabry‐Perot cavity with cleaved end facets and sawed sidewalls. In this study, it is shown that the lowering of the external efficiency is probably associated with the excitation of internally circulating modes, analogous to those found in lasers with four cleaved sides. A dual‐cavity diode structure is employed to demonstrate that it is the sidewall loss which controls the excitation of the internally circulating modes. To determine the geometric conditions for internal mode excitation in single and double heterojunction diodes, an extensive study was made of the combination of length, width, and facet reflectivity which lead to efficiency decreases. It is assumed that the internal modes are excited when the distribute...

Metallurgical amd electroluminescence characteristics of vapor-phase and liquid-phase epitaxial junction structures of InxGa1−xAs

InxGa1−xAs (x = 0.05 to 0.32) p-n junction structures have been grown on GaAs substrates by vapor-phase epitaxy (VPE) and liquid-phase epitaxy (LPE). It is shown that by step-grading the VPE material, lattice-mismatch strain can be absorbed by dislocations at the grading interfaces, leaving the final constant-composition device layers relatively dislocation free. In contrast, the dislocation density for LPE InxGa1−xAs increases with increasing InAs concentration. For both materials, diffusion lengths, electroluminescence efficiencies, and 77°K laser-diode parameters (threshold and efficiency) can be correlated with their dislocation densities. The VPE materials have electrical and luminescence properties that are independent of InAs concentration, and match those of their GaAs counterparts. The LPE materials exhibit properties that degrade with increasing InAs concentration.

Very low‐threshold double‐heterojunction AlxGa1−xAs injection lasers

Double‐heterojunction AlxGa1−xAs lasers have been prepared with a compositional discontinuity Δx at the heterojunctions of 0.45–0.68 and active region widths of ∼0.1 μm. These devices have the lowest room‐temperature threshold current densities (475 A/cm2) yet reported, with a differential quantum efficiency of 40% or more.