Influence of buffer layer material on InGaAs FET optimisation

A study was performed to investigate whether the noise performance of delta-doped heterostructure-insulated-gate FETs (HIGFETs) is adequate for optical receiver applications. The suitability of gate insulator and buffer layers of both AlInAs and InP was investigated. The former has the wider bandgap and will thus give better confinement and lower gate leakage currents, whereas InP has the prospect of reduced trapping and thus of lower noise. The test structures and experimental procedures are described, and the results are discussed. It is found that the lower trap density of InP buffer layers does result in better noise performance if the bias conditions are chosen to minimize the effect of the poorer carrier confinement of InP.<>