The I-V characteristics of the individual subcells of a monolithic Ga 0.50 In0.50 P/ Ga0.99 In0.01 As/Ge triple-junction solar cell have been extracted from measurements of the electroluminescence peak intensity as a function of the electroluminescence injection current. By using the spectral reciprocity relation between the electroluminescence and the quantum efficiency, the individual subcell I-V characteristics were derived. It is shown that the subcell dark I-V characteristics and the subcell illuminated I-V characteristics are accessible under variable spectral illumination conditions
The impact of the thickness of an AlN spacer in AlGaN/AlN/GaN high electron mobility transistor (HEMT) structures on the Hall mobility was investigated in a range of 30 K - 340 K. The AlN spacer has a strong impact on the mobility at temperatures below 150 K. This effect is linked to a reduction of alloy scattering. Optical and scanning electron microscopy revealed hexagonal shaped defects which also have an effect on the mobility. These defects can be avoided by an appropriate adjustment of the AlN layer thickness.
We present temperature dependent magnetoresistance measurements on the 2-dimensional electron gas of epitaxially grown AlGaN/GaN heterojunctions on silicon (Si). We report on the quantum correction to the classical conductance. In particular we found weak localization, electron-electron-interaction, and Shubnikov-de Haas oscillations. The results verify the high material quality of the investigated GaN on silicon.
The electrically active deep levels in a graphene / silicon carbide field effect transistor (FET) were investigated by drain-current deep level transient spectroscopy (ID-DLTS). An evaluation procedure for ID-DLTS is developed in order to obtain the activation energy, the capture cross section and the trap concentration. We observed three defect centers corresponding to the intrinsic defects E1/E2, Ei and Z1/Z2 in n-type 6H-SiC. The determined parameters have been verified by conventional capacitance DLTS.
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