Structural and electrical properties of rectifying p-ZnO/n(+)-InP heterojunction

ZnO thin films were deposited over n(+) InP (100) substrates by Pulsed Laser Deposition (PLD) technique at 400 degrees C temperature in an oxygen ambient of 75 mTorr followed by Rapid Thermal Annealing (RTA) at the temperatures 450 C, 550 degrees C and 650 degrees C respectively. XRD results revealed that the full width at half maxima (FWHM) of the annealed samples were narrower (0.1836) compared to that of the as grown sample (0.3264) for the c-axis oriented ZnO (002) films. A lower strain (similar to-0.23%) and less biaxial compressive stress (similar to-1.063 GPa) were observed for the annealed samples. AFM images depicted lowest surface roughness of 7.257 nm (root-mean-square) for the film annealed at 550 degrees C. A high absorption coefficient of 28.12 mu m(-1) was calculated around 380 nm wavelength from the UV/VIS spectroscopy in reflection mode for the as-grown sample. The optical band gap was calculated to be about 3.23 eV. p-type ZnO film, grown under same condition (annealed at 550 degrees C) over semi insulating InP (100) substrates had a high hole concentration of 2.95X10(19) cm(-3) and Hall mobility of 8.63 cm(2)/V-s at room temperature. Current Rectification Ratio (I(F)/I(R))(|V|=1.5) of 17.2 was measured from the I-V characteristics of the p-ZnO/n(+)-InP heterojunction diode fabricated with the ZnO film annealed at 550 degrees C