Characteristics of two-stage ?-gate on AIGaAs/lnGaAs/AIGaAs DH-HEMTs by using AIGaAs/lnGaP etching-stop layers

摘要

Al_(0.22)Ga_(0.78)As/In_(0.18)Ga_(0.82)As/Al_(0.22)Ga_(0.78)As double heterojunction high electron mobility transistors (DH-HEMTs) with gate structures of traditional planar gate (PG), one-stage gamma-gate (1S?G) and two-stage gamma-gate (2S?G) formed by using the Al_(0.22)Ga_(0.78)As/In_(0.49)Ga_(0.51)P etch-stop layers (ESL) are simulated and presented in this work. Based on this proposed ESL structure design, the fabrication and implementation of studied DH-HEMT device with 1S?G and 2S?G could be expected. Both ?G-structure devices show the better electric field property compared to PG-device. Simulated results reveal that there are no significant differences in common-source voltage-current characteristics among all studied devices. The obtained drain current density and transconductance of all studied devices are about 220 mAmm~(-1) and 265 mSmm~(-1). However, the current stability of ?G-devices with larger bias operation would be improved due to its edge-effect of ?G extended-region. In addition, the electric field intensity under the gate-footprint is effectively reduced by both studied ?G structures. The electric field peak value of PG-device is 498 kV cm"1, and it would be reduced down to about 210 kVcm~(-1) and 178 kVcm~(-1) for 1S?G- and 2S?G-device, respectively. On the other hand, some frequency property dropping is observed from studied device with 1S?G or 2S?G due to the side-edge extension of ?G-device would create the additional parasitic capacitance. The obtained cut-off frequencies are 15 GHz, 10.5 GHz and 10 GHz for PG-, 1S?G- and 2S?G-device (at V_(Gs)=+5 V and V_(Gs)=-0.75 V), respectively.