S. C. Shen

Application of GaAs/GaAlAs multiple-quantum-well infrared detector array in the infrared imaging camera

A long-wavelength (λp=7.7μm) infrared imaging camera that uses a GaAs/GaAlAs multiple-quantum-well infrared photo-detector array is presented. A good infrared image of a group of buildings and trees is demonstrated.

Hydrogenic impurities in two-dimensional circular confined systems at arbitrary magnetic fields

Abstract The magnetic field strength and the circular radius dependences of the ground and excited state energies of a hydrogenic donor in two-dimensional circular confined systems are investigated by a two-point Pade approximation. Our results show that the regime where the magnetic field can be treated as a perturbation increases with decreasing radius of the circle.

Influence of the cap layer thickness on photoluminescence properties in strained InGaAs/GaAs single quantum wells

The influence of the GaAs cap layer thickness on the luminescence properties in strained In0.20Ga0.80As/GaAs single quantum well (SQW) structures has been investigated using temperature-dependent photoluminescence (PL) spectroscopy. The luminescence peak is shifted to lower energy as the GaAs cap layer thickness decreases, which demonstrates the effect of the GaAs cap layer thickness on the strain of InGaAs/GaAs single quantum wells (SQW). We find the PL quenching mechanism is the thermal activation of electron hole pairs from the wells into the GaAs cap layer for the samples with thicker GaAs cap layer, while in sample with thinner GaAs cap layer exciton trapping on misfit dislocations is dominated.

Photothermal ionization spectroscopy for shallow impurities in ultra-pure silicon

We report the comprehensive results obtained in our group and last few years for the shallow impurities in ultrapure silicon by use of photothermal ionization spectroscopy. The new results reported here include the discovery and investigation of new shallow impurity centers in Si, the detection for the compensation of different types of impurities, the accurate determination for the spin-orbit splitting Δ. of valence band for Si, and the phonon duplicates and Fano resonance for the transitions of shallow impurities in Si. In addition it is also shown experimentally that the sensitivity of the photothermal ionization spectroscopy as used for detecting the concentration of shallow donors in Si can reach as high as 108 cm−3, much higher than that reported in the literatures up to date, and line width for the sharpest spectral lines in the spectrum is about 0.08 cm−1, that is, 10 μeV.

Modification of Drude model on the free carrier property of IV-VI compound semiconductor in magnetic field

AbstractA general analytical expression is reported for the Drude models dielectric function of free carrier in multi-valley IV-VI compound semiconductor in the magnetic field. The modifications of the energy band non-parabolicity and free carrier re-population are introduced to the dielectric function in combination with then

optical and transport properties of δ-doped pseudomorphic AlGaAs/InGaAs/GaAs structures

vec k cdot vec P

Effects of an external magnetic field on shallow donor levels in semiconductors.

n model. The difference of the dielectric function between the modified Drude model and the classical Drude model is demonstrated by the calculation for the typical IV-VI compound semiconductor material PbTe.

Long-wavelength optical phonons in Zn1-xMnxSe.

We report for the first time the modulated cyclotron resonance of electrons in the lattice-matched multi-quantum well structures of In0.53Ga0.47As/InP induced by monochromatic light beam of excitation. The resonant enhancement and modulation of the cyclotron resonance of electron due to interband and exciton excitation in the structures have been observed experimentally, which shows the possible prospect of the method for the observation of cyclotron resonances in semiconductors.