Growth and characterization of GaN-based LED wafers on La_(0.3)Sr_(1.7)AITaO6 substrates

摘要

High-quality GaN-based light emitting diode (LED) wafers on La_(0.3)Sr_(1.7)AITaO6 (LSAT) (111) substrates have been demonstrated by molecular beam epitaxy (MBE) for the first time. The structural properties and optoelectronic properties of as-grown LED wafers have been characterized by high-resolution X-ray diffraction (HRXRD), high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), photoluminescence (PL), and electroluminescence (EL). The small full-width at half-maximum (FWHM) values for both symmetric (0002) and asymmetric (1012) HRXRD rocking curves indicate that LED wafers on LSAT (111) substrates are of high crystalline quality, the clear and pronounced Pendellosung fringes of XRD from as-grown multiple quantum wells (MQWs) suggest abrupt InGaN/GaN interfaces with designed layer periodicity and the well controlled composition and thickness of each barrier and well layer with the MQWs, which has also been confirmed by HRTEM characterization. The XRD reciprocal space map (RSM) of the (1015) plane was used to further study the stress state in GaN-based LED wafers. AFM reveals high quality surface morphology for the GaN-based LED wafers on LSAT substrates, with a root-mean-square (RMS) roughness of 1.6 nm, The PL spectrum shows the band edge emission at 445 nm with a FWHM of 24.0 nm. The EL edge emission is observed at 448 nm with a FWHM of 22.6 nm at an injection current of 20 mA, with the light output power of 4.3 mW and the forward voltage of 3.18 V for the chip size of 300 x 300 μm~2, indicating good optoelectronic properties of as-grown GaN-based LEDs on LSAT substrates. This achievement reveals the tremendous potential of GaN-based LEDs on LSAT (111) for optoelectronic device applications.