DC AND RF CHARACTERISTICS FLUCTUATION OF INALAS/INGAAS HEMTS ACCORDING TO THE OPERATING TEMPERATURE VARIATION

Abstract

InAlAs/InGaAs high electron mobility transistors (HEMTs) are a type of field effect transistor that
can achieve extremely high high-frequency gain owing to quantum effects operating in the channel layer. HEMTs
are important components for devices that involve millimeter waves and high-speed optical transmission systems.
However, InAlAs/InGaAs HEMTs have a frequency dispersion that depends on carrier recombination within the
device. This is an InGaAs-specific phenomenon, which degrades the device’s high-frequency gain performance.
In this study, we investigated the direct current (DC) and radio frequency (RF) characteristics of InAlAs/InGaAs
HEMTs by varying the operating temperature from liquid nitrogen temperature to 125 °C. The DC characteristics
showed an increase of the device transconductance (Gm) at low temperature. Reducing the operating temperature
from 125 °C to liquid nitrogen temperature increased Gm to 60 mS. High-frequency gain was also confirmed in
the RF characteristics. The current gain cutoff frequency was 50.2 GHz at room temperature, and 66.8 GHz at
liquid nitrogen temperature, representing an increase of 33.1%. Analyzing the high-frequency characteristics
showed that the high-frequency gain increase at low temperature was related to the temperature dependence of the
parasitic capacitance.