Reduction of sidegating in GaAs analog and digital circuits using a new buffer layer

Abstract

Sidegating effects relevant to GaAs digital, analog, and monolithic microwave integrated circuits have been significantly reduced or eliminated by using a new low-temperature buffer layer grown by molecular-beam epitaxy. At radio frequencies the low-temperature buffer layer reduced the signal coupling between devices, which is an important consideration in microwave integrated circuits. For digital circuit applications, the low-temperature buffer layer eliminated the dependence of the voltage level of an inverter on the logic state of adjacent devices and on the duty cycle of a pulse train encountered in the circuit. The highly resistive nature of the low-temperature buffer enables us to experimentally identify the role that a buffer layer plays in sidegating.

SEU design considerations for MESFETs on LT GaAs

“…Holes diffuse toward but are retained and not recombined. Channel modulation is observed from this large ow much char between a 100A The [12]. Related work on implementing LT GaAs buffers in HIGFETs has shown equivalent device performance with AlGaAs and AlAs [6].…”

“…This not only limits charge collection but reduces backgating effects in GaAs FETs, which are also dominated by holes (and hole traps) in the substrate [12]. The efficiency of the LT GaAs buffer to absorb excess holes is regulated by the potential of the diffusion barriers and the capability of providing a high recombination current inside the buffer.…”

Defect studies in low-temperature-grown GaAs

“…Figure 1.3 shows a schematic cross section r· of a typical MESFET structure fabricated on Sl GaAs illustrating the space charge regions (Chen, et al 1989). For a typical MESFET, Ids of .…”

Picosecond photoconductivity using a graded bandgap Al/sub x/Ga/sub 1-x/As active detecting layer

“…E )qL (4) respectively. The brackets around the mobility account for the fact that the mobility depends on Al fraction, thus is averaged over the graded structure.…”

“…Since the lattice of the L T GaAs layer maintains its crystalline characteristics, epitaxial layers suitable for active GaAs devices can be grown on the L T buffer layer (4,5). With this capability, a photodetector structure which utilizes a high mobility active detecting region, yet takes advantage of a highly defective layer to facilitate picosecond recombination, can be realized.…”