Application of high ϵ paramagnetic and ferroelectric materials to high-transconductance HFETs with low noise and low gate current [InGaAs-AlGaAs devices]

Paraelectric or hysteresis-free ferroelectric gate insulation is ideal for special HFETs meeting bandwidth requirements from 0 to 100 GHz. It allows total suppression of gate leakage currents, while also assuring a large increase in the transconductance of the device at frequencies under 100 MHz, where the permittivity is still high. The gradual decrease of ε in the UHF region is actually very useful, since it limits the free fall of the input impedance of the device to zero, which would load the source excessively. Finally, the lower temperature BaMgF₄ technology avoids oxidation and degradation of the compound semiconductors, and a further improvement in ε through mobile ferroelectric micro-domains is possible by optimizing the growth conditions