Channel Modification of Metamorphic HEMT for Improved Breakdown Characteristics

In this study, we have performed channel modification of theconventional MHEMT (metamorphic high electron mobility transistor)to improve the breakdown characteristics. The modified channelconsists of an In$_x$Ga$_{1-x}$As channel and an InP sub channel instead ofthe In$_x$Ga$_{1-x}$As channel. Since InP has a lower impact ionizationcoefficient in comparison with In$_{0.53}$Ga$_{0.47}$As, we have adopted anInP-composite channel in the modified MHEMT. We have investigatedthe breakdown mechanism and the RF characteristics for theconventional and the InP-composite channel MHEMTs. From themeasurement results, we have obtained enhanced on- and off-statebreakdown voltages of 2.4 and 5.7 V, respectively. Also, theincreased RF characteristics have brought about a decreased outputconductance for the InP-composite channel MHEMT. The cut-offfrequency ($f_T$) and the maximum oscillation frequency ($f_{max}$) for theInP-composite channel MHEMT were 160 GHz and 230 GHz, respectively. It has been shown that the InP-composite channel MHEMT has potentialapplications for millimeter wave power devices. KCI Citation Count: 2