Electrical properties and transport mechanisms of InP/InGaAs HBTs operated at low temperature

The electrical properties of InP/InGaAs HBTs have been comprehensively investigated between room and near liquid helium temperature. Physical mechanisms for the devices operated in different temperature ranges have been clearly identified. The low temperature measurements indicate that, in the temperature range of 240 K to 300 K, the base current is dominated by electron-hole band-to-band recombination; in the temperature range 77 K to 240 K, trap-related recombination (Shockley-Read-Hall recombination) plays an important role in determining base current; and for temperature lower than 77 K, the collector and base currents are found to be limited by electron tunneling through the barrier formed by the conduction-band discontinuity at the E-B junction. These findings provide us with better physical insight of the device operation at low temperature, which is particularly important for the optimization of InP HBT technology for low temperature applications as well as the development of a quantitative model for circuit design