The design and projected performance of quantum-well infrared photodetectors (QWIP) for the terahertz (1–10 THz) or the very-far-infrared region are presented together with our initial demonstration of a GaAs/AlGaAs QWIP working at photon energies below the optical phonons. We point out the problem with this initial device, discuss possible causes, and suggest areas of improvement.

Articles you may be interested inEnhanced efficiency in near-infrared inorganic/organic hybrid optical upconverter with an embedded mirror

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Although the AlxGa1−xAs alloy system has been extensively investigated, there are still considerable uncertainties in measuring the value of x. Here a new AlxGa1−xAs calibration structure, grown by molecular beam epitaxy, has been used to establish unambiguous alloy compositions. Such “standard’’ AlxGa1−xAs layers were measured by high-resolution x-ray diffraction, photoluminescence, and Raman spectroscopy to determine the compositional variations of the measured physical parameters. The phenomenological equations derived from these measurements can now be used to establish the Al content of unknown alloys with confidence. In addition, the results show that Vegard’s law does not hold for the variation of the AlxGa1−xAs lattice constant with x. The small quadratic term has very important implications for a correct analysis of x-ray results.

Abstract-We analyze the high-temperature continuous-wave performance of 1.3-m AlGaInAs/InP laser diodes grown by digital alloy molecular-beam epitaxy. Commercial laser software is utilized that self-consistently combines quantum-well bandstructure and gain calculations with two-dimensional simulations of carrier transport, wave guiding, and heat flow. Excellent agreement between simulation and measurements is obtained by careful adjustment of material parameters in the model. Joule heating is shown to be the main heat source; quantum-well recombination heat is almost compensated for by Thomson cooling. Auger recombination is the main carrier loss mechanism at lower injection current. Vertical electron escape into the -doped InP cladding dominates at higher current and causes the thermal power roll-off. Self-heating and optical gain reduction are the triggering mechanisms behind the leakage escalation. Laser design variation is shown to allow for a significant increase in the maximum output power at high temperatures.Index Terms-Laser thermal factors, optoelectronic devices, quantum-well devices, semiconductor device modeling, semiconductor laser.

We report results of a scanning spreading resistance microscopy ͑SSRM͒ and scanning capacitance microscopy ͑SCM͒ study of the distribution of charge carriers inside multi-quantum-well ͑MQW͒ buried heterostructure ͑BH͒ lasers. We demonstrate that individual quantum-well-barrier layers can be resolved using high-resolution SSRM. Calibrated SSRM and SCM measurements were performed on the MQW BH laser structure, by utilizing known InP dopant staircase samples to calibrate the instrumentation. Doping concentrations derived from SSRM and SCM measurements were compared with the nominal values of both p-and n-doped regions in the MQW BH lasers. For n-type materials, the accuracy was bias dependent with SSRM, while for SCM, excellent quantitative agreement between measured and nominal dopant values was obtained. The SSRM was able to measure the dopant concentration in the p-type materials with ϳ30% accuracy, but quantitative measurements could not be obtained with the SCM. Our results demonstrate the utility of combining calibrated SSRM and SCM to delineate quantitatively the transverse cross-sectional structure of complex two-dimensional devices such as MQW BH lasers, in which traditional one-dimensional probing using secondary ion mass spectroscopy provides only a partial picture of internal device structure.

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Achieving a high internal quantum efficiency in GaAs∕AlGaAs based light-emitting diodes (LEDs) for room-temperature operation at low current-density injection is crucial for applications such as optical up-converters based on the integration of LEDs and photodetectros. We report the experimental results as well as the theoretical analyses of the internal quantum efficiency of GaAs∕AlGaAs LEDs as a function of the p-doping concentration of the active region for low current injection operation. By optimizing the doping concentration, we have achieved a close to 100% internal quantum efficiency for room-temperature operation of LEDs in the low injection current-density range, i.e., around 0.1A∕cm2. An optical up-converter was fabricated using wafer-fusion technology by integrating the optimized GaAs∕AlGaAs LED with an InGaAs∕InP photodetector. The internal up-conversion quantum efficiency was measured to be 76%.