The Study of GaN PN-Junction Grown on Si Substrate by MBE with Ni/Ag as Ohmic Contact

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) omega/2 theta scans of (0002) plane at room temperature is 0.34 degrees. 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 E-2 (low), E-1 (high) and A(1) (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 E-1 (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.