Study of the n~+ GaN Cap in AlGaN/GaN High Electron Mobility Transistors with Reduced Source-Drain Resistance

摘要

An n~+ GaN cap layer has been applied on an AlGaN/GaN high electron mobility transistor (HEMT) to achieve a non-alloyed ohmic contact. Delta dopings were used at the heterointerface of the n~+ GaN cap and AlGaN layer to lower the AlGaN potential barrier and to improve communication between the n~+ GaN cap and the two-dimensional electron gas (2DEG) channel. Non-alloyed ohmic contact resistance as low as 0.2 Ω· mm, and sheet resistance of 60 Ω/□ were achieved. Selective etch and sidewall technology were applied during processing. The n~+ capped device was fabricated and compared to a standard AlGaN/GaN HEMT. Lower on-resistance and access resistance, higher f_τ and f_(max), and better linearity in terms of g_m were achieved.