Plasma assisted molecular beam epitaxy of AlGaN/GaN high electron mobility transistors

We report on the plasma-assisted molecular beam epitaxy (PAMBE) of AlGaN/GaN high electron mobility transistors (HEMTS). Growth was performed on MOCVD grown GaN Templates and 4H-SiC(0001) wafers with 3 diameter. In a detailed study of GaN growth conditions the growth rate was varied between 0.28 and 0.5 µm/h. Under optimized conditions, the surface root mean square roughness was less than 0.6 nm. Low temperature PL measurements in the range 1.9 to 3.8 eV showed only the exciton-emission with a FWHM of 12 meV. AlGaN-HEMT structures on GaN-templates exhibited room temperature Hall mobilities of 1600 cm2/Vs and sheet electron concentration of 8 × 1012/cm2. On SiC mobilities of 1220 cm2/Vs were achieved. Current-voltage output characteristics of PAMBE grown AlGaN/GaN HEMTs on SiC showed a drain current density about 0.8 A/mm for a gate bias of +1V and only small dispersion