B.I. Miller

Variation of minority‐carrier diffusion length with carrier concentration in GaAs liquid‐phase epitaxial layers

Minority‐carrier diffusion lengths in GaAs at 298 K were determined in Ge‐doped p‐type layers and Sn‐doped n‐type layers by short‐circuit photocurrent measurements. The layers were grown by liquid‐phase epitaxy and utilized a 1‐ to 2‐μ top layer of Al0.5Ga0.5As to eliminate surface recombination. Electron diffusion lengths Ln of 7–8 μ were obtained at concentrations less than 1×1018 holes/cm3 with a decrease to 0.8 μ at 1×1019 holes/cm3. Hole diffusion lengths Lp of 2–4μ were obtained at concentrations less than 1×1018 electrons/cm3 with a decrease to 0.3 μ at 6×1018 electrons/cm3. The relatively constant diffusion length in p‐ and n‐type layers below concentrations of 1×1018 cm−3 is determined by nonradiative recombination. At hole concentrations above 1×1018 cm−3, the radiative recombination contributes to the decrease in Ln. For the n‐type layers, the rapid decrease in Lp above concentrations of 1×1018 cm−3 results from an increase of nonradiative recombination at high donor concentrations.

Tapered waveguide InGaAs/InGaAsP multiple-quantum-well lasers

The use of ultrathin etch-stop techniques to expand the vertical optical mode size adiabatically in 1.5- mu m InGaAs/InGaAsP MQW lasers using a tapered-core passive intracavity waveguide structure is discussed. 30% differential quantum efficiency out the tapered facet, far-field FWHM of approximately 12 degrees and a butt-coupling efficiency into a cleaved fiber of -4.2 dB, with -1-dB alignment tolerances of approximately +or-3 mu m, were achieved.<<ETX>>

Studies in Selenious Acid Reduction and CdSe Film Deposition

The reaction sequence for the reduction of in at various surfaces and the formation of selenide films in this medium with and without metal ions present have been investigated by rotating disk and ring‐disk electrode techniques. The system is complicated by competitive paths leading to selenium formation from Se(−2)‐Se(+4) chemical reactions and the result is sensitive both to the nature of the substrate with the possibility of metal selenide formation and to the concentration of solution species. The implications for cathodic deposition of semiconductors like , from voltammetric and photospectral data, are discussed.

Monolithic two‐section GaInAsP/InP active‐optical‐resonator devices formed by reactive ion etching

Narrow, high‐aspect‐ratio grooves formed by reactive ion etching (RIE) are shown to be useful as partially transmissive mirrors for coupled active laser‐detector, laser‐modulator, and laser‐etalon two‐section monolithic devices. Results emphasize control of the longitudinal mode spectrum by active etalon action.

A 16*1 wavelength division multiplexer with integrated distributed Bragg reflector lasers and electroabsorption modulators

The integrated operation of a 16*1 wavelength-division-multiplexed (WDM) source with distributed Bragg reflector (DBR) lasers and electroabsorption modulators has been demonstrated. By using repeated holographic exposures and wet chemical etching, 16 different wavelengths from 1.544 to 1.553 mu m with an average channel spacing of 6 AA are obtained. A high-performance combiner is used to obtain a very uniform coupling into the single-output waveguide, and with the integration of an optical amplifier an average optical power of -8 dBm per channel is coupled into a single-mode fiber.<<ETX>>

Efficiency of broadband four-wave mixing wavelength conversion using semiconductor traveling-wave amplifiers

We present a theoretical analysis and experimental measurements of broadband optical wavelength conversion by four-wave mixing in semiconductor traveling-wave amplifiers. In the theoretical analysis, we obtain an analytical expression for the conversion efficiency. In the experiments, both up and down-conversion efficiencies are measured as a function of wavelength shift for shifts up to 27 nm. The experimental data are well explained by the theoretical calculation. The observed higher conversion efficiency for wavelength down-conversion is believed to be caused by phase interferences that exist between various mechanisms contributing to the four-wave mixing process.<<ETX>>

Electric field screening by photogenerated holes in multiple quantum wells : a new mechanism for absorption saturation

We observe saturation in the electroabsorption of InGaAs/InP multiple quantum wells (MQWs) at high optical intensity. Contrary to the mechanism for zero‐field MQWs, we find that saturation occurs due to the presence of trapped photogenerated holes that screen the MQWs from the applied electric field. By carefully measuring the absorption coefficient of the wells and the emission time for holes, we are able to fit the observed electroabsorption saturation with no adjustable parameters.

Four-wave mixing wavelength conversion efficiency in semiconductor traveling-wave amplifiers measured to 65 nm of wavelength shift

The efficiency of broadband optical wavelength conversion by four-wave mixing in semiconductor traveling-wave amplifiers is measured for wavelength shifts up to 65 nm using a tandem amplifier geometry. A quantity we call the relative conversion efficiency function, which determines the strength of the four-wave mixing nonlinearity, was extracted from the data. Using this quantity, gain requirements for lossless four-wave mixing wavelength conversion are calculated and discussed. Signal to background noise ratio is also measured and discussed in this study.<<ETX>>

Reduction of GaAs surface recombination velocity by chemical treatment

Chemisorbed ruthenium ions on the surface of n‐GaAs decrease the surface recombination velocity of electrons and holes from 5×105 to 3.5×104 cm/sec. It is shown that the ions, in a one‐third monolayer thickness, are confined to the surface and do not form a new junction by diffusing into the GaAs. This use of Ru appears to be the first observation of the reduction of the surface recombination velocity for GaAs by the simple chemisorption of ions.

GaInAsP/InP stripe‐geometry laser with a reactive‐ion‐etched facet

We report the first use of reactive‐ion etching (RIE) to form mirror facets on GaInAsP/Inp double‐heterostructure (DH) lasers (λ∼1.3 μm). The RIE, performed with a Cl2:O2 gas mixture, provides vertical etched walls with no undercutting. Initial laser results demonstrate that quasi‐single‐mode operation and reasonable threshold currents are possible.