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A calculation is presented for the direct conversion of a measured luminescence signal to the implied open circuit voltage. The effects of re-absorption, spectral dependence, and interference with front and back interfaces are all included, so long as the optical properties of the structure are known. The method is validated through a comparison of the terminal open-circuit voltage with the photoluminescence intensity of Cu(In,Ga)Se2 solar cells, each as a function of illumination intensity. [ABSTRACT FROM AUTHOR]

CdSeTe/CdMgTe double heterostructures were produced with both n-type and unintentionally doped absorber layers. Measurements of the dependence of photoluminescence intensity on excitation intensity were carried out, as well as measurements of time-resolved photoluminescence decay after an excitation pulse. It was found that decay times under very low photon injection conditions are dominated by a non-radiative Shockley-Read-Hall process described using a recombination center with an asymmetric capture cross section, where the cross section for holes is larger than that for electrons. As a result of the asymmetry, the center effectively extends photoluminescence decay by a hole trapping phenomenon. A reduction in electron capture cross section appeared at doping densities over 1016cm-3. An analysis of the excitation intensity dependence of room temperature photoluminescence revealed a strong relationship with doping concentration. This allows estimates of the carrier concentration to be made through a non-destructive optical method. Iodine was found to be an effective n-type dopant for CdTe, allowing controllable carrier concentrations without an increased rate of non-radiative recombination. [ABSTRACT FROM AUTHOR]

A recent article [A. Bejan, A. Almerbati, and S. Lorente, J. Appl. Phys. 121, 044907 (2017)] takes note of a relationship between size and efficiency that appears in the performance data of many engines and power plants. The authors attempt to interpret this phenomenon thermodynamically, concluding that the relationship is predicted by a general thermal power plant model. However, this conclusion is the result of an elementary error. The efficiency of the idealized thermal model in fact stays constant or decreases with increasing size. [ABSTRACT FROM AUTHOR]

A recent paper [A. Bejan and R. W. Wagstaff, J. Appl. Phys. 119, 094901 (2016)] concludes that bodies of the same size suspended uniformly in space are in a state of high internal tension. The tension is then relieved by rearrangement of the bodies into a non-uniform distribution of mass. In this Comment, it is shown that the conclusions are based upon calculations which are in error, and that the amount of tension is not in fact decreased by such a rearrangement. [ABSTRACT FROM AUTHOR]

Double heterostructures (DH) were produced consisting of a CdTe film between two wide band gap barriers of CdMgTe alloy. A combined method was developed to quantify radiative and nonradiative recombination rates by examining the dependence of photoluminescence (PL) on both excitation intensity and time. The measured PL characteristics, and the interface state density extracted by modeling, indicate that the radiative efficiency of CdMgTe/CdTe DHs is comparable to that of AlGaAs/GaAs DHs, with interface state densities in the low 1010cm-2 and carrier lifetimes as long as 240 ns. The radiative recombination coefficient of CdTe is found to be near 10-10 cm³s-1. CdTe film growth on bulk CdTe substrates resulted in a homoepitaxial interface layer with a high non-radiative recombination rate. [ABSTRACT FROM AUTHOR]

A magnetoresistance method is proposed which extracts both the growth direction mobility and the planar mobility of an anisotropic thin film, such as a superlattice. A magnetic field which varies in magnitude and orientation is employed. Errors appearing in previous magnetotransport studies on superlattices are resolved. In particular, it is shown that the contact layers used to send currents through an active region do not have a negligible resistance, even if they are much more conductive than the active region. The technique is demonstrated on an InAs/GaSb-based structure where the growth axis to planar mobility anisotropy ratio is found to drop rapidly with increasing temperature. [ABSTRACT FROM AUTHOR]

Variable magnetic field Hall effect, photoluminescence, and capacitance-voltage (CV) analysis have been used to study InN layers grown by plasma assisted molecular beam epitaxy. All three techniques reveal evidence of a buried p-type layer beneath a surface electron accumulation layer in heavily Mg-doped samples. Early indications suggest the Mg acceptor level in InN may lie near 110 meV above the valence band maximum. The development of p-type doping techniques offers great promise for future InN based devices. [ABSTRACT FROM AUTHOR]

The valence band offset of wurtzite InN(0001)/yttria stabilized cubic-zirconia (YSZ)(111) heterojunctions is determined by x-ray photoemission spectroscopy to be 1.19±0.17 eV giving a conduction band offset of 3.06±0.20 eV. Consequently, a type-I heterojunction forms between InN and YSZ in the straddling arrangement. The low lattice mismatch and high band offsets suggest potential for use of YSZ as a gate dielectric in high-frequency InN-based electronic devices. [ABSTRACT FROM AUTHOR]

High-quality (0001) and (0001¯)-GaN films were grown by plasma-assisted molecular-beam epitaxy to study the dependence of oxygen incorporation on polarity and oxygen partial pressure. Oxygen incorporates at a rate ten times faster on nitrogen-polar GaN than on the Ga polarity. Oxygen doping is controllable, reproducible, and produces low compensation material up to concentrations of at least 10[sup 18] cm[sup -3] with higher levels showing significant compensation. Layers containing oxygen at levels above 10[sup 22] cm[sup -3] exhibit severe cracking while oxygen concentrations less than 10[sup 21] cm[sup -3] do not introduce significant strain. The oxygen incorporation rate has a weak dependence on Ga overpressure during Ga-stable growth but dramatically increases for conditions approaching N-stable growth. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]