Threshold behavior in backgating in GaAs metal-semiconductor field-effect transistors: Induced by limitation of channel-substrate junction to leakage current

An analytical model is proposed to understand backgating in GaAs metal-semiconductor field-effect transistors (MESFETs), in which the effect of channel-substrate (CS) junction is included. We have found that the limitation of CS junction to leakage current will cause backgate voltage to apply directly to CS junction and result in a threshold behavior in backgating effect. A new and valuable expression for the threshold voltage has been obtained. The corresponding threshold electric field is estimated to be in the range of 1000-4000 V/cm and for the first time is in good agreement with reported experimental data. More, the eliminated backgating effect in MESFETs that are fabricated on the GaAs epitaxial layer grown at low temperature is well explained by our theory. (C) 1997 American Institute of Physics.

Morphology Evolution of (331)A High-Index Surfaces During Atomic Hydrogen Assisted Molecular Beam Epitaxy (MBE)

Step like morphology of (331)A high-index surfaces during atomic hydrogen assisted molecular beam epitaxy (MBE) growth has been investigated. Atomic Force Microscope (AFM) measurements show that in conventional MBE, the step heights and terrace widths of GaAs layers increase monotonically with increasing substrate temperatures. The terrace widths and step densities increase with increasing the GaAs layer thickness and then saturates. And, in atomic hydrogen assisted MBE, the terrace width reduces and density increases when depositing the same amount of GaAs. It attributes this to the reduced surface migration length of Ga adatoms with atomic hydrogen. Laterally ordered InAs self-aligned nano-wires were grown on GaAs (331)A surfaces and its optical polarization properties were revealed by photoluminescence measurements.

Frequency limitation in calibrating microwave test fixtures

The problem of frequency limitation arising in calibration of the test fixtures is investigated in this paper. It is found that at some frequencies periodically, the accuracy of the methods becomes very low, and. the denominators of the expressions of the required S-parameters approach zero. This conclusion can be drawn whether-the test fixtures, are symmetric or not. A good agreement between theory and experiment is obtained.