Huang Qi

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.

Detection of 36Cl with accelerator mass spectrometry

An accelerator mass spectrometry (AMS) system based on the HI-13 tandem accelerator at the Institute of Atomic Energy (IAE) is described, and the first detection of 36Cl with our AMS system is reported. The electrostatic deflector completely rejects isotopic background, 35Cl and 37Cl. The ioinzation chamber distinguishs 36Cl from isobaric background, 36S. The measurement of 36Cl with two samples is presented.

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.

Normal-incidence quantum well infrared photodetector without grating coupler

The n-type GaAs/AlxGa1-xAs multiple quantum well infrared photodetectors have been demonstrated without any grating couplers. We have achieved a responsivity Rv of 1.7 × 105 V/W and a detectivity Dλ* of 4.0×1010 cmsq-Hz/W for a wavelength of 8.4 μm at a temperature T = 77 K in normal incidence.

Magnetic Depopulation of Subbands in Very Narrow Quantum Channels

A model for electrons confined in narrow conducting channels in the presense of a magnetic field is presented which takes into account a cut-off in the filling of the subbands. Such a cut-off gives rise to energy separated subbands resulting in a relation between sublevel index n and inverse magnetic field B-1 such that in the high field regime it envolves into an original form as in a 2D case and in the moderate field regime it shows pronounced deviation from linearity.