Current Power Characteristics Research Articles

Local thermoelectric effects in wide-gap semiconductors

Experimental confirmation of the appearance of local thermal electromotive forces, which were previously found in structures based on silicon p–n junctions, is obtained. The current–voltage and frequency characteristics of an asymmetric potential barrier at the GaN/Mg boundary and of a p–i–n structure based on GaAs are studied. It is shown that, similarly to wide-gap semiconductors, the contribution of local thermal electromotive forces determines the features of the current–voltage characteristics and the frequency features of the current–power characteristics, in particular the Gaussian resonance. Proper account and use of local thermoelectric forces makes it possible to attain a drastic increase in the efficiency of thermoelectric conversion and an improvement in the operating parameters of microelectronic components.

High-Performance AlGaInP/GaAs Light-Emitting Diodes with a Carbon-Doped GaP/Indium–Tin Oxide Contact Layer

An alternative heavily carbon-doped GaP (GaP:C) contact layer is demonstrated to form a good ohmic contact to electron-beam-evaporation indium–tin oxide (ITO) spreading layer on the AlGaInP light-emitting diode (LED) with a GaAs absorbing substrate. The LEDs with GaP:C/ITO contact layer provide a substantial improvement in light output power over conventional structures (without GaP:C/ITO). The AlGaInP LEDs with GaP:C/ITO structures exhibited a higher external quantum efficiency (3.24%) and larger light output power (5.9 mW) under a dc operation of 160 mA than those of 2.01% and 1.93 mW at 120 mA for the conventional structures, showing an earlier saturation behavior of current-power characteristics. These positive results are tentatively attributed to the introduction of the GaP:C/ITO current-spreading structures in the LEDs.

Ultraviolet photodetectors based on natural diamond

Ultraviolet photodetectors based on natural 2a diamond are fabricated and examined. From the capacitance-voltage characteristics and capacitance spectra, it is found that the ac conductivity of photodetectors is purely capacitive and that the capacitance of the samples is determined by their geometry. The dynamic range of the photodetectors is found to be no less than 104. The measured photosensitivity spectra and current-power characteristics bear evidence of the high sensitivity and selectivity of the photodetectors in the UV region, which favor their application for the detection of weak radiation signals, including detection during day-time.

Light emitting diodes for the spectral range of λ=3.3–4.3 μm fabricated from the InGaAs-and InAsSbP-based solid solutions: Electroluminescence in the temperature range of 20–180°C

Light emitting diodes (LEDs) with λmax=3.4 and 4.3 µm (t=20°C) were studied at elevated temperatures. It is demonstrated that LEDs operating in the temperature range t=20–180°C can be described using the classical concepts of injection radiation sources and the processes of charge carrier recombination. The temperature dependences of reverse currents in the saturation regions of current-voltage characteristics are consistent with the increase in the intrinsic-carrier concentration according to the Shockley theory. The emission spectra are described on the assumption of the direct band-to-band transitions, spherically symmetric bands, and thermalized charge carriers. The current-power characteristics are proportional to I3/2 suggesting that the contribution of the nonradiative Auger recombination is dominant. The radiation power decreases exponentially with the temperature which is characteristic of the CHSH and CHCC processes.

Dominance of auger recombination in InGaAsP light emitting diode current-power characteristics

Output power saturation in 1.3-µm InGaAsP light emitting diodes with various active layer thickness has been investigated experimentally in a wide temperature range. Nonradiative recombination current with strong injected carrier density dependence, which is responsible for saturation, was found to be proportional to active layer thickness and almost independent of temperature under constant injected carrier density conditions. External quantum efficiency at a constant injected carrier density was found to be independent of active layer thickness. These results indicate strongly that Auger recombination is the dominant nonradiative process in InGaAsP light sources.

Properties of planar stripe-geometry heterojunction lasers. I. Nonlinear and discontinuous current-power characteristics

Studies were made of some features of the current-power characteristics of cw planar stripe-geometry AlGaAs-GaAs heterojunction lasers and of the influence of temperature (from – 60 to + 60 °C) and diode resonator length (0.2–0.7 mm) on these characteristics. Current-power characteristics with radiation power nonlinearities, nonmonotonic behavior, discontinuities (jumps), and hysteresis loops were observed. It was found that when the temperature changes, the features of the current-power characteristics may change substantially and the degree of nonlinearity tends to increase as the temperature and resonator length increase. At the same time, it was noted that the critical power of a step on the nonlinear current-power characteristic changes negligibly. In contrast, the critical power for the appearance of power jumps and hysteresis decreases substantially with temperature. An analysis is made of a phenomenological model for the formation of hysteresis loops of current-power characteristics.

Properties of planar stripe-geometry heterojunction lasers. II. Analysis of electrical characteristics

An investigation was made of differential current-voltage characteristics of cw planar stripe-geometry heterojunction lasers at room temperature. In these lasers, the current-power characteristics frequently have anomalies in the form of nonlinearities, nonmonotonic behavior discontinuities, and power hysteresis loops. It is shown that these characteristics are accompanied by certain features of the electrical characteristics, for example, of the function IdU/dl, where U is the voltage across the diode and I is the pump current. Thus, by observing the current-voltage characteristics, it is possible to identify anomalies in the laser action without optical measurements. If the photoelectric effect inside the diode does not mask the fundamental relationship between the optical and electrical characteristics, an anticorrelation is observed between the differential resistance and the differential efficiency of the laser. An analysis is made of an idealized model of the current-voltage characteristic of an injection laser and a modification of this model is used to interpret (at least qualitatively) the observed relationship between the current-voltage and current-power characteristics.