AlInAs/GaInAs HEMT with AlInP barrier layer

Due to its high frequency and noise performances, AlInAs/GaInAs/InP HEMT is a very good candidate for high bit rate optical communications or millimeter-wave circuits applications. Transistors with impressive cut-off frequencies have been demonstrated. However, the use of these devices is plagued by excess gate leakage current and low breakdown voltage originating from impact ionization in the low energy bandgap GaInAs channel. Moreover, a fine adjustment of the gate recess depth has proven to be very difficult, impacting the control of the transistor pinch-off voltage and its homogeneity over the wafer. In order to reduce these deleterious effects, improvements in the transistor structure have been proposed, and the insertion of a semiconductor layer with appropriate characteristics between the transistor gate and channel has proven to be a valuable solution.