Small Signal Modeling And Parameter Extraction Of Millimeter Wave GaN Based HEMT

Because of the unique semiconductor characterization and the great prospect of application of GaN material, GaN HEMT havs become the current research focus. Suitable GaN HEMT small-signal equivalent circuit model is essential for analysing the device properties and designing the MMIC circuit. At the process of achieving mesa edge on GaN Epitaxial wafers, the dry etch process causes mesa edge lattice damage, then affect of DC and microwave characteristics of the GaN device.By analyzing the DC and microwave test data of 90 nm gate length AlGaN/GaN HEMTs and 200 nm gate length InAlN/GaN HEMTs, we have found the change of f T depend on the mesa edge effect. Based on the above considerations, we established a small signal model which considers mesa etch effect. The CMEE is extracted by regarding CMEE and the intrinsic capacitance of Cgs as a whole. For 90 nm gate length AlGaN/GaN HEMTs and 200 nm gate length InAlN/GaN HEMTs, the CMEE are 5.1fF and 1.3fF, respectively. By analyzing the date of frequency characteristics of GaN HEMT and establish small-signal equivalent circuit model of the, reached the following conclusions.Mesa etching effect is the main factor affecting the frequency characteristics of the device. By testing a 90 nm gate length AlGaN / GaN HEMTs S-parameters we can get the fT of 2 × 20μm gate width AlGaN/GaN HEMTs which is 59.2GHz and 2×50μm gate width which is 78.6GHz, an increase of 32.8%. The simulated f T obtained after de-embedding CMEE of 2×20μm gate width AlGaN/GaN HEMTs is 78.7GHz grow to 2×50μm gate width AlGaN/GaN HEMTs of 83.6GHz, an increase of 6.2%.Impact of mesa etching effect in the small gate width device is stronger than the large gate width device. In the gate width of 2×20μm of AlGaN/GaN HEMTs devices, embedded CMEE go after fT ratio obtained by simulation test S-parameters extrapolated fT growth of 32.9%; gate width of 2×50μm of AlGaN/GaN HEMTs devices after the simulation was to insert CMEE fT S-parameters ratio test parameters extrapolated fT increase of 6.4%.