Analysis of a radio frequency transimpendance amplifier based on a δ-doped AlInAs-GaInAs HEMT and its performance optimization

A simple approach has been proposed for the optimization of performance parameters such as transimpedance-bandwidth product, transition frequency f_T and maximum frequency of oscillation f_max of high electron mobility transistors (HEMTs). The radio frequency (RF) small-signal equivalent circuit model has been employed to represent the ac behavior of T-shape gate AlInAs-GalnAs delta-doped HEMTs. All the circuit parameters pertaining to the model have been determined as a function of the width W of the device and surface density of charge delta in the channel. Then PSpice has been used to simulate the device. Good agreement between experimental and simulated values of |h_fe|² versus frequency is obtained. The same model is then employed to optimize performance parameters of the HEMT and the MSM-HEMT amplifier with reference to width and surface density of charge delta in the channel.