The refractive indices of AlxGa1−xAs epitaxial layers (0.176⩽x⩽1) are accurately determined below the band gap to wavelengths, λ<3 μm. The layers are grown on GaAs substrates by molecular beam epitaxy metal organic and chemical vapor deposition with thicknesses ranging from 4 to 10 μm. They form improper waveguide structures with the GaAs substrate. The measurements are based on the excitation of the improper waveguide modes with grating couplers at 23 °C. The refractive indices of the layers are derived from the modal propagation constants in the range of 730 nm<λ<830 nm with an estimated uncertainty of Δn=5×10−4. The temperature coefficient of the refractive index is investigated in the same spectral range. From the effective indices of the TE and TM modes, we derive the strain-induced birefringence and the elasto-optic coefficients. High-resolution x-ray diffraction is used to determine the strain of the layers. The layer compositions are obtained with inductively coupled plasma atomic emission spectro...

The refractive index of AlxGa1−xAs below the band gap: Accurate determination and empirical modeling

The authors propose and analyze the traveling-wave photodetector (TWPD), an edge-coupled photodetector that is capable of both a larger absolute bandwidth and a larger bandwidth-efficiency product than the waveguide photodetector (WGPD). The intrinsic RC bandwidth limitation is increased in the traveling-wave photodetector by providing for controlled transmission of the electrical wave down the device in parallel with the optical wave and by eliminating bandwidth-limiting electrical reflections. It is shown that 1- mu m wide, parallel-plate, GaAs/AlGaAs, p-i-n TWPD with open-circuit input termination has a 26% greater potential bandwidth-efficiency product than the comparable WGPD, while a TWPD with matched input termination actually has a worse bandwidth-efficiency product than the WGPD. >

Traveling-wave photodetectors

MOBILEs (monostable-bistable transition logic elements), which have the advantages of multiple-input and multiple-function, are demonstrated in InP-based material system using monolithic integration of resonant-tunneling diodes and high electron mobility transistors. The high peak current density, high peak-to-valley ratio, and high transconductance, which are required for high-performance MOBILEs, are demonstrated in this InP-based material system. A fabricated MOBILE with three-input gates having 1:2:4 width ratio can perform weighted-sum threshold logic operation, and has a wide range of applications in new computing architectures, such as neural networks.

InP-based high-performance monostable-bistable transition logic elements (MOBILEs) using integrated multiple-input resonant-tunneling devices

Sacrificial etching of III - V compounds is reviewed with emphasis on its use in surface micromachining of micromechanical structures. A table is presented with 23 different combinations of stopping layers, sacrificial layers, and etchants for sacrificial etching of GaAs- and InP-based epitaxial heterostructures. Examples of surface micromachined microstructures of III - V compounds are shown, and some possible applications are discussed.

http://iopscience.iop.org/article/10.1088/0960-1317/6/4/003/pdf

Sacrificial etching of III - V compounds for micromechanical devices

60 nm InAs high-electron-mobility transistors (HEMTs) with a thin channel, a thin InAlAs barrier layer, and a very high gate stem structure have been fabricated and characterized. The thickness of the channel, as well as that of the InAlAs barrier layer, was reduced to 5 nm. A stem height of 250 nm with a Pt-buried gate was used in the device configuration to reduce the parasitics. A high DC transconductance of 2114 mS/mm and a current-gain cutoff frequency (fT) of 710 GHz were achieved at VDS=0.5 V.

https://iopscience.iop.org/article/10.7567/APEX.6.034001/pdf

InAs thin-channel high-electron-mobility transistors with very high current-gain cutoff frequency for emerging submillimeter-wave applications

Etching studies involving citric acid/hydrogen peroxide (C 6 H 8 O 7 :H 2 O 2 ) at volume ratios from 0.5: 1 to 50: 1 were found to provide good selective etching of various III-V semiconductor materials grown on GaAs and InP substrates using molecular beam epitaxy. Both selective and uniform (nonselective) etching regions were found between these material systems by choosing different concentration volume ratios of citric acid/hydrogen peroxide (χC 6 H 8 O 7 :1H 2 O 2 )

Wen F. Tseng

Papers

Etch Rates and Selectivities of Citric Acid/Hydrogen Peroxide on GaAs , Al0.3Ga0.7As , In0.2Ga0.8As , In0.53Ga0.47As , In0.52Al0.48As , and InP

Etch Rates and Selectivities of Citric Acid/Hydrogen Peroxide on GaAs, Al0.3Ga0.7As, In0.2Ga0.8As, In0.53Ga0.47As, In0.52Al0.48As, and InP.