High-growth-rate AlGaN buffer layers and atmospheric-pressure growth of low-carbon GaN for AlGaN/GaN HEMT on the 6-in.-diameter Si substrate metal-organic vapor phase epitaxy system

Abstract

In this study, we investigated the effects of growth pressure on incorporation of carbon in GaN and on the growth rate of AlGaN using a multiwafer (7×6in.) mass-production metal-organic vapor phase epitaxy (MOVPE) reactor. In the two-dimensional electron gas (2DEG) region of an AlGaN/GaN high electron-mobility transistor (HEMT) structure, a high GaN purity is required. The incorporation of carbon in GaN could be easily controlled over a carbon concentration range of three orders of magnitude by varying pressure. Thus, the reactor can be used for growth at both reduced pressure and atmospheric pressure. Furthermore, an AlGaN growth rate of over 1μm/h was demonstrated for Al composition in the range of 0.3–0.8 by suppressing the gas-phase prereaction between the precursor materials. An AlGaN/GaN HEMT structure was also demonstrated. The magnitude of wafer bowing was less than 50μm. The full widths at half maximum (FWHMs) of the X-ray rocking curve (XRC) of GaN were 570″ in the GaN (002) direction and 760″ in the GaN (102) direction. The sheet carrier density and Hall mobility were 1.056×1013cm−2 and 1550cm2/Vs, respectively.