GaN-based optoelectronic devices on sapphire and Si substrates

A recessed gate AlGaN/GaN high-electron mobility transistor (HEMT) on sapphire (0 0 0 1), a GaN metal-semiconductor Field-effect transistor (MESFET) and an InGaN multiple-quantum well green light-emitting diode (LED) on Si (I 1 1) substrates have been grown by metalorganic chemical vapor deposition. The AlGaN/GaN intermediate layers have been used for the growth of GaN MESFET and LED on Si substrates, A two-dimensional electron gas mobility as high as 9260 cm(2)/V s with a sheet carrier density of 4.8 x 10(12)cm(-2) was measured at 4.6 K for the AlGaN/GaN heterostructure on the sapphire substrate. The recessed gate device on sapphire showed a maximum extrinsic transconductance of 146 mS/mm and a drain-source current of 900 mA/mm for the AlGaN/GaN HEMT with a gate length of 2.1 mum at 25degreesC. The GaN MESFET on Si showed a maximum extrinsic transconductance of 25 mS/mm. and a drain-source current of 169 mA/mm with a complete pinch-off for the 2.5-mum-gate length. The LED on Si exhibited an operating voltage of 18 V, a series resistance of 300 Omega, an optical output power of 10 muW and a peak emission wavelength of 505 nm with a full-width at half-maximum of 33 nm at 20 mA drive current. (C) 2002 Published by Elsevier Science Ltd.