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) 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.