In this paper, using a fully-coupled, three-dimensional electro-thermal device simulator, we study the mechanism of efficiency degradation at high current operation in planar GaN-based light emitting diodes (LED). In particular, the improvement of the efficiency degradation using thicker conductive GaN substrates has been demonstrated. First, it is found that local Joule heating inside thin conduc...
X-ray topographic and chemical etching examination of Si:Ge single crystals containing 1.2 at% and 3.0 at% Ge, together with precise lattice parameter measurements, was performed. Diffraction contrasts in the form of concentric `quasi-circles' (striations), probably due to the non-uniform distribution of Ge atoms, were observed in projection topographs. The etching patterns reveale...
We present a non-contact method for the determination of the thermal response time of temperature sensors embedded in wafers. In this method, a flash lamp illuminates a spot on the wafer in periodic pulses; the spot is on the opposite side from the sensor under test. The thermal time constant of the sensor is then obtained from measurement of its temporal response, together with a theoretical mode...
Using plasma enhanced chemical vapor deposition (PECVD) at 13.56 MHz, a seed layer is fabricated at the initial growth stage of the hydrogenated microcrystalline silicon germanium (μc-Si1−xGex:H) i-layer. The effects of seeding processes on the growth of μc-Si1−xGex:H i-layers and the performance of μc-Si1−xGex:H p—i—n single junction solar cells are investigated. By applying this seeding method, ...
Orthogonal experiments of GaSb films growth on GaAs substrate have been designed and performed by using a low-pressure metal–organic chemical vapor deposition (LP-MOCVD) system. The crystallinities and microstructures of the produced films were comparatively analyzed to achieve the optimum growth parameters. It was demonstrated that the optimized GaSb thin film has a narrow full width at half maxi...
For homogeneous materials, the ultrasonic immersion method, associated with a numerical optimization process mostly based on Newton's algorithm, allows the determination of elastic constants for various synthetic and natural composite materials. Nevertheless, a principal limitation of the existing optimization procedure occurs when the considered material is at the limit of the homogeneous hypothe...
The bonding-temperature-dependent lasing characteristics of 1.5 a µm GaInAsP laser diode (LD) grown on a directly bonded InP substrate or Si substrate were successfully obtained. We have fabricated the InP substrate or Si substrate using a direct hydrophilic wafer bonding technique at bonding temperatures of 350, 400, and 450 °C, and deposited GaInAsP or InP double heterostructure layers on this I...
A contactless non-destructive imaging method for spatially resolved dopant concentration, [2.2] N d, and electrical resistivity, ρ, of n- and p-type silicon wafers using lock-in carrierography images at various laser irradiation intensities is presented. Amplitude and phase information from wafer sites with known resistivity was employed to derive a calibration factor for accurate determination of...
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