Локализация носителей заряда в квантовых ямах InGaN/GaN, ограниченная объемным зарядом

The mechanism of carrier tunneling through the potential walls of InGaN/GaN quantum well in the p-n structures is studied by means of the deep center tunneling spectroscopy. A number of humps on the current and photocurrent tunneling spectra, as well as on the forward bias dependences of the intensity and the peak energy of photoluminescence band from the quantum well are detected. These findings allow us to propose a model of carrier localization in the quantum well that permit to relate the tunneling transparency of the potential walls of the QW to the space-charge of deep-level centers in the quantum well barriers and its changes under optical excitation and forward biasing of p-n structure.

Dark current and 1/f noise in forward biased InAs photodiodes

Dark current and low-frequency noise have been studied in forward biased InAs photodiodes within the temperature range 77…290 K. Photodiodes were fabricated by diffusion of Cd into n-InAs single crystal substrates. It has been shown that, at the temperatures >130 K, the forward current is defined by recombination of charge carriers with participation of deep states in the middle of band gap. At these temperatures, a correlation is found between forward current and 1/f noise. At lower temperatures, the forward current and noise have been analyzed within the model of inhomogeneous p-n junction caused by dislocations in the depletion region. The experimental evidence has been obtained that multiple carrier tunneling is the main transport mechanism at low temperatures, which leads to an increase in low-frequency noise.

Experimental and Modeling Study on the High-Performance p++-GaAs/n++-GaAs Tunnel Junctions with Silicon and Tellurium Co-Doped InGaAs Quantum Well Inserted

The development of high-performance tunnel junctions is critical for achieving high efficiency in multi-junction solar cells (MJSC) that can operate at high concentrations. We investigate silicon and tellurium co-doping of InGaAs quantum well inserts in p++-GaAs/n++-GaAs tunnel junctions and report a peak current density as high as 5839 A cm−2 with a series resistance of 5.86 × 10−5 Ω cm2. In addition, we discuss how device performance is affected by the growth temperature, thickness, and V/III ratio in the InGaAs layer. A simulation model indicates that the contribution of trap-assisted tunneling enhances carrier tunneling.

Low Resistance TiO2/p-Si Heterojunction for Tandem Solar Cells

Niobium-doped titanium dioxide (Ti1−xNbxO2) films were grown on p-type Si substrates at low temperature (170 °C) using an atomic layer deposition technique. The as-deposited films were amorphous and showed low electrical conductivity. The films became electrically well-conducting and crystallized into the an anatase structure upon reductive post-deposition annealing at 600 °C in an H2 atmosphere for 30 min. It was shown that the Ti0.72Nb0.28O2/p+-Si heterojunction fabricated on low resistivity silicon (10−3 Ω cm) had linear current–voltage characteristic with a specific contact resistivity as low as 23 mΩ·cm2. As the resistance dependence on temperature revealed, the current across the Ti0.72Nb0.28O2/p+-Si heterojunction was mainly determined by the band-to-band charge carrier tunneling through the junction.

Ferroelectric-Semiconductor Solar Cells: An Alternative Configuration With High-Efficiency

The power generation of conventional solar cells suffers from their low open-circuit voltages that are restricted by the bandgap of employed semiconductors. We propose a novel photovoltaic cell based on the combination of ferroelectric materials and conventional semiconductors to overcome this restriction. In the proposed configuration, a semiconductor slab sandwiched between two parallel polarized ferroelectric materials attains an electric field parallel to the interfaces leading to an above-bandgap voltage across the semiconductor. Furthermore, the configuration allows the charge carriers produced in the semiconductor to be transported within the semiconductor to the contacts without having to cross the semiconductor-ferroelectric interface. The power generation is expected to be higher than those of conventional solar cells and previously studied combined designs: (i) Firstly because its open-circuit voltage can be much higher, as it is not restricted by the bandgap of the semiconductor material; (ii) secondly because certain unfavorable carrier transport processes, such as carrier tunneling through the interface and carrier transport through the low-mobility ferroelectric material, are not part of the circuit.

An asymmetric hot carrier tunneling van der Waals heterostructure for multibit optoelectronic memory

Novel optoelectronic memory is fabricated using a van der Waals heterostructure of PtS2/h-BN/graphene with asymmetric hot carrier tunneling barriers.

Температурное падение эффективности мощных синих InGaN/GaN-светодиодов

The thermal droop of external quantum efficiency (EQE) at maximum in blue InGaN/GaN LEDs at j < 10 A/cm2 is caused by increasing losses related to non-radiative recombination due to carrier tunneling with the assistance of phonons and traps, enhancing by a temperature growth up to 400 K. When a p-n junction opens at j > 40 A/cm2, the EQE droop under direct current and at pulse mode is due to the losses associated with non-equilibrium filling of the states related to lateral alloy non-uniformities in quantum wells situated outside of the depletion region by delocalized carriers as well as the losses due to the interactions between delocalized carriers and extended defects.