Characterization of AlGaN/GaN high electron mobility transistors on GaN substrates with different thicknesses of GaN channel and buffer layers using side-gate modulation

AlGaN/GaN high electron mobility transistors (HEMTs) on GaN substrates with different thicknesses of GaN channel and C-doped buffer layers were fabricated and characterized with conventional DC and side-gate (SG) measurements. In SG measurement, drain current (I (D)) was measured while SG bias (V (SG)) was applied through a separate SG contact that surrounds the device active region. Whereas all HEMTs have comparable DC measurement results (similar to 500 mA mm(-1) I (D), -2 V threshold voltage and similar to 130 mS mm(-1) transconductance), SG measurements show drastically different performances among the samples. Comparing HEMTs with and without C-doped buffer layer, results demonstrate that HEMT with doped buffer was stable against SG modulation until -15 V V (SG), whereas the HEMT without doped buffer was modulated near 0 V, and hence unstable against SG bias. Comparing HEMTs different channel thicknesses, the HEMT with a thicker 900 nm channel was more resistant to SG modulation than the HEMT with a thinner 100 nm channel. Therefore, these results highlight the importance of buffer doping and channel thickness to buffer stability.