Threshold Coupling AlGaN/GaN HEMT Incorporating a Composition-Modulated Barrier for High-Voltage and High-Linearity Application

In this work, a threshold coupling (TC) AlGaN/GaN high-electron-mobility transistor (HEMT) incorporating a composition-modulated Al _x Ga ${}_{\text {1-}{x}}$ N barrier (CM.TC HEMT) distinguished by 100 V high-linearity operation has been proposed. Al composition (Al%) was pertinently designed in the barrier to accomplish charge redistribution, thus mitigating electric field (E-field) crowding in the recessed part of a conventional TC structure (Con.TC HEMT) and addressing its diminished linearity effectiveness under high operating voltages. As a result of the epitaxial optimization, transconductance ( ${G}_{\text {m}}$ ) roll-off with increased drain biases was suppressed, and the breakdown voltage ( ${V}_{\text {BK}}$ ) was improved from 152 to 298 V. In 3.6 GHz large signal measurement with a drain voltage ( ${V}_{\text {DS}}$ ) of 48 V, the CM.TC HEMT demonstrated comparable saturated output power density ( ${P}_{\text {sat}}$ ) to the Con.TC HEMT, while achieving a 6% higher peak power-added efficiency (PAE) and a 3 dB improvement in output third-order intercept point (OIP3). 100 V single and two-tone evaluation further revealed a ${P}_{\text {sat}}$ of 14.7 W/mm and an OIP3 of ~42.7 dBm for the CM.TC HEMT. The reported device extends the linearity benefits originally enjoyed by moderate voltages to an elevated scenario, which is promising for serving power amplifiers (PAs) that require both high-linearity and high-voltage operation.