Zhou Jun-Ming

Characteristics of GaN grown on 6H-SiC with different AlN buffers

Characteristics of GaN grown on 6H-SiC (0001) substrates using different thicknesses of AlN buffers are studied. It is found that the surface morphology and crystal quality of GaN film closely depends on the strain state of the AlN buffer. For a thicker AlN buffer, there are cracks on GaN surface, which make the GaN films unsuitable for applications. While for a thinner AlN buffer, more dislocations are produced in the GaN film, which deteriorates the performance of GaN. Possible generation mechanisms of cracks and more dislocations are investigated and a ~100 nm AlN buffer is suggested to be a better choice for high quality GaN on SiC.

Effect on transport properties of electrons at modulation-doped GaAs/AlGaAs heterostructure interface by neutron irradiation

It has been found that after the irradiation by fast neutrons the electron density and mobility of two-dimensional (2D) electron gas at modulation-doped GaAs/AlGaAs heterostructure interface increased by 17% and 23%, respectively, and the Hall plateaus and the minima of Shubnikov-de Haas (S-dH) oscillation curves anomalously shifted over each other. The measurements after three weeks showed that the effects mentioned above had disappeared substantially, however, the stronger persistent photoconductivity still remained.

The behaviour of Si in AlXGa1-XAs grown by MBE

With the use of RHEED, a new surface reconstruction AlxGa1-xAs (001)-(3×2) induced by Si dopant, and a Si dopant effect for suppressing island growth and promoting layer by layer growth are observed.

The measurement on magnetophonon resonance of 2d electron system in GaAs-AlxGa1-xAs heterostructure interface

The 2D magnetophonon oscillatory in GaAs-AlxGa1-xAs hetero-structure interface, grown by MBE, has been investigated by means of the second derivative of the magnetoresistance under high pulsed magnetic fields up to 40T. The fundamental magnetic field has been measured as 23.7T and the damping facter γ, 2D electron effective mass m* for our sample are 1.58 and 0.0747me, respectively.

Growth and Characteristics of Epitaxial AlxGa1−xN by MOCVD

AlxGa1-xN epilayers with a wide Al composition range (0.2 ≤ x ≤ 0.68) were grown on AlN/sapphire templates by low-pressure metalorganic chemical vapour deposition (LP-MOCVD). X-ray diffraction results reveal that both the (0002) and (105) full widths at half-maximum (FWHM) of the AlxGa1−xN epilayer decrease with increasing Al composition due to the smaller lattice mismatch to the AlN template. However, the surface morphology becomes rougher with increasing Al composition due to the weak migration ability of Al atoms. Low temperature photoluminescence (PL) spectra show pronounced near band edge (NBE) emission and the NBE FWHM becomes broader with increasing Al composition mainly caused by alloy disorder. Meanwhile, possible causes of the low energy peaks in the PL spectra are discussed.

Study of the properties of infrared intersubband transition in doped GaAs/AlxGa1-xAs multiple quantum wells

The properties of intersubband transition of GaAs/AlxGa1-xAs multiple quantum wells with various well widths and doped-well concentrations have been studied. Both theoretical and experimental results are in good agreement. For the appropriate well width and higher doping concentration, we directly observed two intersubband absorption peaks from E1 → E2 and E2 → E3 transitions in well. The experimental results and theoretical analysis are given.

Photoluminescence studies of In0.25Ga0.75As-GaAs strained quantum wells under high pressure

We report the results of the photoluminescence (PL) studies of the In0.25Ga0.75As-GaAs strained quantum wells (QWs) at 77K and at high pressures up to 50kbar. The pressure coefficients of the Γ valley of (InGa)As-GaAs strained QWs are presented for the first time. The crossover between the energy level in the well and the X valley in the barrier GaAs has been observed. The ratio of the conduction band offset to valence band offset in In0.25Ga0.75As-GaAs heterojunction was determined to be Qc=ΔEc:ΔEv=0.68:0.32. Some discussions about GaAs-Al0.3Ga0.7As QWs are also presented.

REGROWTH OF MBE-GAAS FILMS ON SI SUBSTRATES BY HIGH-ENERGY ION-IMPLANTATION AND SUBSEQUENT ANNEALING

4.2 Me V 7Li channeling technique, laser Raman scattering spectrometry, and TEM have been utilized to study the regrowth of MBE-GaAs films of similar μm thick on Si substrates by Si+ implantation (0.6-2.6 MeV) and subsequent rapid thermal annealing. The results showed that crystalline disorder was greatly reduced in the recrystalized layers especially at the interface.

ELECTRO-LUMINESCENCE AND PHOTO-LUMINESCENCE FROM STRAINED SiGe/Si QUANTUM WELL

Photo-luminescence and electro-luminescence from step-graded index SiGe/Si quantum well grown by molecular beam epitaxy is reported. The SiGe/Si step-graded index quantum well structure is beneficial to the enhancing of electro-luminescence. The optical and electrical properties of this structure are discussed.

Two-Wave Mixing in Resonant Photorefractive GaAs/AlGaAs Semi-insulating Multiple Quantum Wells

We have observed the two-wave mixing of the photorefractive GaAs/AlGaAs semi-insulating multiple quantum wells fabricated by film lift-off approach and protonimplanting technique. Under the non-optimized condition, we have obtained the two-wave mixing gain larger than 180 cm-1 at wavelength near 784 nm for a field of 10 kV/cm. Energy transfer is also observed when the applied field is perpendicular to the grating vector.