Nitride-based devices fabricated by wet etching

Photo-enhanced chemical (PEC) wet etching technology was used to etch GaN and AlGaN epitaxial layers. Figure 1 shows PEC etch rate for the GaN and Al_xGa_1-xN epitaxial layers in aqueous KOH and H₃PO₄ solutions. It was found that the maximum etch rates were 510 nm/min, 1960 nm/min, 300 nm/min and 0 nm/min for GaN, Al_0.175Ga_0.825N, Al_0.23Ga_0.77N and Al_0.4Ga_0.6N, respectively. Nitride-based Schottky diodes and heterostructure field effect transistors (HFETs) were also fabricated by PEC wet etching. As shown in figures 2, 3 and 4, it was found that we could achieve a saturated I_D larger than 850 mA/mm and a maximum g_m about 163 mS/mm from PEC wet etched HFET with a 0.5μm gate length. Compared with dry etched devices, the leakage currents observed from the PEC wet etched devices were also found to be smaller.