Compound semiconductor devices for communication applications

Breathtaking progress in key compound semiconductor devices have led to amplifiers exhibiting extremely low noise, high efficiency and high frequency of operation which in turned have paved the way for their use in low power and wireless communication applications. Among them are modulation doped FETs and heterojunction transistors. MODFETs utilizing strained channels of InGaAs on GaAs and on InP have noise figures less than 0.2 dB at 10 GHz, and power added efficiencies in excess of 60% at about 5 GHz. Low noise and high power efficiency attainable lend this technology to, among others, satellite uplink and downlink systems and cellular wireless communication. Due to the higher electron mobility and velocity accorded InGaAs-InP heterostructure system, current gain cutoff and maximum oscillation frequencies of 172 and 328 GHz were obtained for drain voltages as low as 1.5 V. Excellent performance can be expected at frequency at or below 60 GHz, well suited for video and voice, and data transmission. In parallel to developments in the MODFET arena, the heterojunction bipolar technology has also made considerable progress to be a formidable contender. Typical results from GaAs based discrete HBTs include a power output of 0.5 W, gain of 11 dB, and power added efficiency of 60%.