Electron gas dimensionality engineering in AlGaN/GaN high electron mobility transistors using polarization

We propose and demonstrate a two dimensional/three dimensional hybrid channel AlGaN/GaN high electron mobility transistor (HEMT) structure with a flat transconductance profile using polarization-induced channel engineering. A quasi three dimensional electron gas profile with 5–6 nm of vertical channel depth was formed by grading the channel region linearly from GaN to Al_0.15Ga_0.85 N over 50 Å. We demonstrate a flat g_m profile in an AlGaN/GaN HEMT with high current density of 1 A/mm and peak g_m of 168 mS/mm over 85% of the input bias range under dc conditions. This approach simultaneously enables vertical device scaling and transconductance engineering in a HEMT structure.