Fabrication of high performance AlGaN/GaN FinFET by utilizing anisotropic wet etching in TMAH solution

Abstract

AlGaN/GaN-based fin-shaped field-effect transistors (FinFETs) with very steep sidewall and various fin-widths (Wfin) have been fabricated by utilizing electron-beam lithography and additional anisotropic sidewall wet etch in tetramethyl ammonium hydroxide (TMAH) solution. The device with Wfin of 180 nm exhibits normally-on performance with threshold voltage of −3.5 V and extremely broad transconductance (gm) characteristic ranging from −2 to ∼ 3 V at Vd = 5 V which is essential for high linearity device performance. This broad gm characteristic is because the current from the side-wall MOS channel becomes comparable to that from the two-dimensional electron gas (2DEG) channel and hence significantly contributes to the total device current. On the other hand, devices with smaller Wfin = 50 and 100 nm exhibit normally-off performance with positive threshold voltage of 2.0 and 0.6 V, respectively, and less broad gm characteristics because the current from the side-wall MOS channel dominates the total device current.