Notes: We present variational calculations of the ground and higher-energy states for (100)Si metal-oxide-semiconductor inversion layers in the electric field induced by the gate voltage as represented by a recently proposed logarithmic potential. The ground-state energies are calculated in the electric quantum limit using the well-known Fang–Howard trial wave function. The higher-energy states are obtained using a Gram–Schmidt orthogonalization approach, beginning with trial wave functions that resemble the Laguerre functions. We compare our results with the standard triangular potential approximation involving the Ai(z) Airy function and its roots.

Notes: The phase and amplitude of the response to infrared radiation of superconducting bolometers was investigated. The detectors were fabricated with 120–550 nm Y1Ba2Cu3O7−δ films on MgO, SrTiO3, and LaAlO3 substrates. A model for the response is developed and compared to the experimental results. The response versus frequency of the samples shows bolometric behavior, in agreement with the measured time dependence of the signals at low frequencies. Different techniques were developed to measure the key parameter in the response of the bolometers, G, the thermal conductance. Several anomalies were observed in the study that provide insight into heat conduction in these devices. The dc or low modulation frequency thermal conductance, G(0), of the samples is found to be limited by the substrate/cold-head thermal boundary resistance. It was also found to decrease with increasing substrate thickness, but still limited by the substrate/cold-head interface. This thickness dependence of G(0) is attributed to scattering of phonons within the substrate, that changes their transmission rate through the substrate/cold-head interface. The results from simultaneous measurements of the IR response and dR/dT (using R versus T) at low modulation frequencies (20 Hz) show that the magnitude of the response differs by up to 30% from the dR/dT curve. The discrepancy is found to be frequency dependent, increasing with decreasing modulation frequency.This can be treated by use of temperature-dependent thermal constants (G and the heat capacity, C) in the model for the bolometric response. The discrepancy is also observed to be dependent on the superconducting transition, which suggests a possible correlation between the heat conduction through the substrate (and its interfaces) and the absorption mechanism in the superconductor. The phase of the response versus temperature shows an abrupt change at the transition. This is evidence for a change in thermal constants in the bolometer as it goes through the superconducting transition, affecting both the phase and magnitude of the response. Joule heating at even high bias currents has little effect on the response (and its deviation from the dR/dT curve) in our samples, and the effect of noise on the response is significant only at very low bias currents. © 1995 American Institute of Physics.

Notes: Meander line patterned infrared detectors, with values of resistance Ronset at the onset temperature Tc onset of 3–5 kΩ, were fabricated from YBa2Cu3O7−x superconducting material on MgO and SrTiO3 crystalline substrates. Noise voltages from the samples were measured versus bias current, radiation modulation frequency, and temperature, in both the normal and superconducting states. Four major types of voltage noise were identified according to where they occurred in temperature relative to Tconset and the zero resistance temperature Tc zero, and their dependence on frequency and bias current. They were also associated with the granularity of the superconducting film, which is related to the substrate material used. From these observations a specific cause for each type of noise is suggested. The results are as follows. (i) In the normal state with temperature T(approximately-greater-than)Tc onset, noise with a magnitude that is consistent with thermal (Johnson) noise is seen, but it depends linearly on bias current above a threshold value, at low frequencies.The suggested noise source is conductivity fluctuations due to Cooper pairs. (ii) Noise was found to occur below Tc zero in granular films. With increasing bias current its magnitude increases, and it shifts to a lower temperature range; however, the noise magnitude becomes constant as the current goes to zero. It is weakly dependent on frequency above 400 Hz. Suggested cause is voltage fluctuations in superconductor–normal–superconductor junctions at grain boundaries. (iii) This noise also occurs below Tc zero with peaks at various temperatures. With increasing bias current the peaked noise spreads to lower temperatures, but the noise goes to zero as the bias current goes to zero. Its suggested cause is magnetic flux tube motion. (iv) This noise occurs between Tc onset and Tc zero and is present in all samples, but lowest on samples prepared on SrTiO3 substrates. Its suggested cause is fluctuations in the volume fraction of the superconducting phase along the current path. While the measured detectivity D* of our samples at a wavelength of 20 μm was only 106 cm Hz1/2/W, engineering changes can be expected to raise the value to above 1010 cm Hz1/2/W. © 1996 American Institute of Physics.

Notes: Results of measurements of the annealing of photodegraded amorphous silicon p-i-n solar cells are presented. The annealing process can be characterized by a relatively fast initial stage followed by a much slower second stage. Although the annealing behavior cannot be described by simple exponential kinetics, it can be characterized by a single activation energy of 1.2 eV. The degradation temperature and the duration of the light soaking do not affect this activation energy, although the ratio of the "fast'' to the "slow'' portions of the recovery change as these experimental parameters are varied. We have explained these phenomena in terms of hydrogen motion in the material.

Notes: A model is presented for heterojunction solar cells, in which interface recombination is the dominant diode current mechanism, that relates the charging of interface states to the voltage dependence of the light-generated current jL(V). The model also shows how a diode ideality factor greater than two can occur. The calculations presented are for the small-signal case, and do not treat the intensity dependence of the collection factor η(V)=jL(V)/jsc. The parameters chosen were such as to account for the trends seen in the CuInSe2/CdS solar cell.