RF Characteristics of AlGaN/GaN HEMTs under Different Temperatures

We present the Rf characteristics of 0.7-mu m gate length n-GaN/AlGaN/GaN high-electron mobility transistors (HEMTs) with different source-drain spacing tested under different temperatures.. The 7-mu m source-drain spacing device demonstrated 800 mA/mm drain current density and 257 mS/mm tranceconductance, and the 5-mu m source-drain spacing device demonstrated 700 mA/mm drain current density and 260 mS/mm tranconductance. The 7-mu m source-drain spacing device was measured at room temperatures of 25 degrees C and -40 degrees C, the current gain (f(T)) were 18 GHz and 21GHz and the maximum oscillation (f(max)(U)) frequency were 63 GHz-and 87 GHz, respectively The f(T) was nearly linearly dependent on the temperature. As operating temperature increased from -40 degrees C to 50 degrees C, the f(T) dropped more dramatically for the 5-mu m SD spacing device than for the 7-mu m device. The f(max) characteristic of 5-mu m SD spacing device decreases more dramatically above 125 degrees C than the 7-mu m SD spacing device. This phenomenon might be due to stronger phonon scattering for shorter channel device at high temperatures.