Improved On/Off Current Ratio and Linearity of InAlN/GaN HEMTs with N2O Surface Treatment for Radio Frequency Application

Abstract

Due to the strong spontaneous polarization, InAlN/GaN high-electron-mobility transistors (HEMTs) offer advantages over conventional AlGaN/GaN HEMTs with a thinner barrier. However, a thin InAlN barrier layer inevitably leads to a high gate leakage current and thus degrades the device performance. Here, we demonstrate a reduced gate leakage current (I g) and an improved on/off current ratio (I ON/I OFF) on a 60-nm-gate-length InAlN/GaN HEMTs on Si by using N2O treatment. The device presents that I g decreases from ∼1 × 10−4 A mm−1 (without N2O) to 5 × 10−6 A mm−1 (with N2O), and I ON/I OFF increases from ∼1 × 105 (without N2O) to ∼1 × 108 (with N2O). The short-channel effects (SCEs) are also suppressed and the drain-induced barrier lowering (DIBL) decreases from more than 120 mV V−1 (without N2O) to 90 mV V−1 (with N2O). In addition, the InAlN/GaN HEMT with N2O treatment shows a flatter trend of transconductance (g m) with gate-source voltage (V gs) and three folds of the gate voltage swing(GVS) increase from 1.6 V (without N2O) to 4.8 V (with N2O), an indication of the improved device linearity. RF performance shows that a current gain cutoff frequency (f T) of 185 GHz is obtained on a 60-nm-gate-length InAlN/GaN HEMTs with N2O treatment. It presents the great potential of N2O surface treatment for the InAlN/GaN HEMTs for radio frequency application.