Jianrong Dong's research while affiliated with Chinese Academy of Sciences and other places

Photoluminescence (PL) investigation was carried out on GaInP/GaAs multiple quantum wells structures grown on (001) and (311) B surfaces of GaAs by gas source molecular beam epitaxy. Superlattice structures of GaAs/GaInP grown on (001) GaAs substrate were also studied in comparison. Deep-level luminescence was seen to dominate the PL spectra from the quantum wells and superlattice structures that were grown on (001) GaAs substrate. In contrast, superior optical properties were exhibited in the same structures grown on (311) B GaAs surfaces. The results suggested that GaAs/GaInP quantum well structures on (311) B oriented substrates could efficiently suppress the deep-level emissions, result in narrower PL peaks indicating smooth interfaces. © 1998 American Institute of Physics.

InAs layers were grown on GaAs by molecular beam epitaxy (MBE) at substrate temperature 450 and 480°C, and the surface morphology was studied with scanning electron microscopy (SEM). We have observed a high density of hexagonal deep pits for samples grown at 450°C, however, the samples grown at 480°C have smooth surface. The difference of morphology can be explained by different migration of cations which is temperature dependent. Cross-sectional transmission electron microscopy (XTEM) studies showed that the growth temperature also affect the distributions of threading dislocations in InAs layers because the motion of dislocations is kinetically limited at lower temperature.

The transport properties of large lattice-mismatched InAs/GaAs heterojunctions were examined. In spite of a high dislocation density at the hetero-interface, very high electronic mobilities are obtained in the InAs film. The mobilities demonstrate a pronounced minimum around room temperature in undoped samples. By doping Si into the layer far from the InAs/GaAs interface, a higher mobility than the undoped sample with the same thickness is always obtained. Such abnormal behavior is explained by the parallel conduction from the quasi-bulk carriers and interface carriers. The high mobility InAs films are found to be suitable materials for making Hall elements.

This paper reports InAs thin films grown on GaAs (001) substrates by Molecular Beam Epitaxy (MBE) with good crystal quality, high electron mobility and small temperature dependence. Hall effect devices with sensitivity 50% higher than that of GaAs planar Hall effect devices are produced by using these films.

GaxIn1-xP(x≈0.51) epilayers grown on (100) GaAs by MOCVD and on (100) and (111)B by GSMBE were characterized by X-ray diffraction and photoluminescence (PL). The 10K PL spectra show that PL peak energies of GaInP on (100) grown by MOCVD and GSMBE are smaller than the band gaps by 104 and 43 meV, respectively, indicating the ordering in the GaInP. This results are explained on the basis of the model proposed by Kurtz et al.. Finally, we also discuss the possibilities of ordering in GaInP on differently oriented GaAs substrates and arrive at the conclusion that the GaInP grown on (111) GaAs is always disordered.

Photoluminescence of GaInP under hydrostatic pressure is investigated. The Γ valley of disordered GaInP shifts sublinearly upwards with respect to the top of the valence band with increasing pressure and this sublinearity is caused by the nonlinear relationship between lattice constant and hydrostatic pressure. The Γ valleys of ordered GaInP rise more slowly than that of the disordered one and the relationship between the band gap and the pressure can not be explained in the same way. Taking into account the interactions between the Γ valley and the folded L valleys, as well as, the X valleys, the experimental pressure dependences of the band gap of ordered GaInP epilayers are calculated and fitted quite well using first order perturbation theory. The results indicate that simultaneous ordering along 〈111〉 and 〈100〉 directions can occur in ordered GaInP.

Photoluminescence of GaInP epilayers under hydrostatic pressure is investigated. The Γ valley of disordered GaInP shifts sublinearly upwards with respect to the top of the valence band with increasing pressure and this sublinearity is caused by the nonlinear dependence of lattice constant on the hydrostatic pressure. The Γ valleys of ordered GaInP epilayers rise slower than that of the disordered one. Considering the interactions between the Γ valley and folded L and X valleys, the pressure dependence of the band gap of ordered GaInP is calculated and fitted. The results demonstrate that not only ordering along 〈111〉 directions but also sometimes simultaneous ordering along 〈111〉 and 〈100〉 directions can occur in ordered GaInP.

MOCVD-grown Ga xIn 1-xP (x=0.476-0.505) epilayers were characterized by double-crystal X-ray diffraction (DCXD), Hall measurement and Photo-luminescence. It is found that Ga composition decreases a little with increasing V/III ratio at 650°C due to the competition between the formation of GaP and InP. The electron mobility of Ga 0.5In 0.5 P reaches 3300cm 2/(V·s) at 77K. The carrier concentration decreases with increasing growth temperature and V/III ratio. It suggests that Phosphorus (P) vacancies act as donors. At 17 K, the difference between PL peak energy and calculated band-gap energy of GaInP is between 84-113 meV. This is probably related to impurities and ordered structure in GaInP.

GaN is an important semiconductor material operating in the blue light range. GaN epitaxial layer was successfully achieved by MOCVD with TMGa and NH 3 as sources on (0112) α-Al 2O 3 substrate. The morphorlogical, crystalline, electrical and optical characterizations of the GaN film were investigated. The minimum FWHM of (2110) peak of double crystal X-ray diffraction rocking curve is 16'. Near ultraviolet and visible light are observed by cathode luminescence.

Single-crystal GaN films have been deposited on () sapphire substrates using trimethylgallium (TMGa) and NH3 as sources. The morphological, crystalline, electrical and optical characterizations of GaN film are investigated. The carrier concentration of undoped GaN increases with decreasing input NH3-to-TMGa molar flow ratio.