Huang Baibiao

Electrical properties and Raman spectra of undoped and Al-doped ZnO thin films by metalorganic vapor phase epitaxy

Abstract Undoped and Al-doped ZnO thin films have been deposited on Si substrates using metalorganic vapor phase epitaxy at atmospheric pressure. The as-deposited ZnO films showed good crystalline character and exhibited (002) orientation with the c axis perpendicular to the substrate surface. The carrier concentration of ZnO films was found to be dependent upon the doping of Al, and varied in the range from 10 19 to 10 20 cm −3 . The resistivity of ZnO films was in the order of magnitude of 10 −3 Ωcm. The Hall mobility decreased with the doping of Al and was in the range 5–53 cm 2 (V·s) −1 . Raman spectra indicated the observed A 1 (LO) and E 2 (high) bands shifted towards the low-frequency side.

Growth of AlxGa1−xP on GaAs substrate by metalorganic vapor phase epitaxy

The crystalline perfection of the AlxGa1−xP film grown on GaAs substrate by atmospheric pressure metalorganic vapor phase epitaxy has been studied using double-crystal X-ray diffraction and back-scattering spectrometry, and the behavior for the optical phonons of the AlxGa1−xP epilayer investigated by the Raman scattering technique. In addition, the reflection spectra in the visible-light spectra region from multilayer structures constructed by AlxGa1−xP/GaP pairs have been measured. The measurement of the full-width at half-maximum of the X-ray diffraction peak of the AlxGa1−xP epilayer showed that the crystalline perfection of the AlxGa1−xP film was improved by growing a GaP buffer layer and using a misoriented GaAs substrate. Corresponding to the temperature range 750–820°C, the higher crystalline perfection was obtained at the lower growth temperature. The value of the minimum yield of back-scattering spectrometry of Al0.24Ga0.76P/GaAs (3.4×10−2) revealed that the epilayer was not perfect and contained both elastic strain and misfit dislocations. A two-mode Raman characteristic of Al0.21Ga0.79P/GaAs was clearly seen with two LO modes, AlP-like LO and GaP-like LO located at 460 and 392 cm−1, respectively. For the (Al0.21Ga0.79P)10/(GaP)10 structure, a reflectivity above 60% was realized.

Crystal characterization of GaP epilayer grown on GaAs by atmospheric pressure metalorganic vapor phase epitaxy

The crystal perfection in GaP film grown on GaAs by atmospheric pressure metalorganic vapor phase epitaxy has been studied by the use of double crystal X-ray diffraction, backscattering spectrometry and Raman scattering techniques. By means of the morphology and full-width at half maximum of X-ray diffraction peak for the GaP epilayers, the growth temperature and V/III ratio were optimized. In the temperature range from 720 to 800°C and with the V/III ratio range from 10 to 80, it was concluded that the optimum growth temperature was 800°C with a V/III ratio of approximately 15. The result of backscattering spectrometry revealed that the minimum yield for the GaP epilayer grown under nearly optimized growth conditions exceeded that for a perfect crystal. In addition, the residual strain of GaP epilayer was calculated by using a biaxial stress model and Raman scattering measurement.

MOCVD Growth of GaAs/AlxGa1-xAs Superlattices and Their Smoothing Effects

This paper presents metalorganic chemical vapor deposition (MOCVD) growth of GaAs/AlxGa1-xAs superlattices in our laboratory. Superlattice structures are characterized by using cross-sectional transmission electron microscopy, and the results show that they are in agreement with designed parameters. The superlattice used as buffer layer can smooth out interface fluctuations. The high mobility of Ga-containing species and the anisotropic growth rate of GaAs on different facets lead to the planarization of the wavy interface, whereas the low mobility of Al-containing species tends to preserve the surface shape.

Study on the stability of GaAs/AlGaAs superlattice structure

This paper reports the stability of GaAs/AlGaAs superlattice structures after thermal annealing, Zn diffusion and MeV Si+ ion implantation. The MeV Si+ ion implantation induced damage in GaAs/AlGaAs superlattices, its annealing properties, and the effects on superlattice structure stability are reported as well. Thermal annealing at 650°C for 30 min has little effect on superlattice structure. Zn diffusion may induce superlattice layer disordering. And annealing at 650°C for 30 min can eliminate damage caused by 2.3 MeV, 1.5×1015 cm-2 Si+ ion implantation, which cannot induce superlattice layer disordering.

Metal-Organic Chemical Vapor Deposition Growth of GaAs/AlAs Double Barrier Resonant Tunneling Diodes

We have grown two structures of AlAs/GaAs/AlAs double barrier resonant tunneling diodes by metal-organic chemical vapor deposition. The resonances to the first excited states were obtained, the measured peak-to-valley current ratio is 1.3 at 77 K, room temperature peak current is 8 kA/cm2, the resonance voltages are in agreement with the theoretical approach by transfer-matrix method.