The study of GaN pn-junction grown on Si substrate by MBE with Ni/Ag as ohmic contact

摘要

The gallium nitride (GaN) pn-junctions was grown on silicon (111) substrate by plasma assisted molecular beam epitaxy (PA-MBE) on top of a AlN buffer in order to reduce the strain of the alloy. For GaN pn-junction layers, silicon and magnesium were used as n and p dopants, respectively. The SEM images show a high quality hetero-interface without cracking by optimizing the growth conditions. The full width at half-maximum (FWHM) of the GaN pn-junctions deposited on silicon as determined by X-ray diffraction (XRD) symmetric rocking curve (RC) ω/2θ scans of (0002) plane at room temperature is 0.34°. Raman results show the maximum intensity at 523.63 cm−1 which is attributed to crystalline silicon. All the allowed Raman optical phonon modes of GaN, i.e. the E2 (low), E1 (high) and A1 (LO) are clearly presented, which are located at 147.76 cm−1, 571.65 cm−1 and 737.9 cm−1, respectively. The presence of E1 (high) has led to the evidence of hexagonal-phase character for this GaN pn-junction layer. The non-existence of yellow band emission in PL result confirmed that the thin film is of good optical quality. The GaN pn-junction diode shows a rectifying behavior of current under forward bias.