In this paper we study the transient and steady-state photoconductivity of semiconductor nanowires by putting forward the importance of surface recombination in the photocurrent formation. The phenomenological model based on existence of radius and time dependent surface band bending is able to explain both the dark conductivity and dynamics of photoconductivity transients in semiconductor nanowires. The dependence of the variation of surface recombination barrier height on the carrier capture by surface states leads to a non- exponential character of photoconductivity kinetics. Analytic equations are derived to calculate current-voltage and lux-ampere characteristics, photocurrent relaxation and gain under the excitation of light pulses. The analytical results are compared with the experimental data.
The idea of the quantum dot solar cell, which provides a novel direction to the high-efficiency solar cell problem, is developed. A theoretical model is presented for a practical p-i-n quantum dot solar cell built on the base of the self-organized InAs/GaAs system. Study the advantages of the use of quantum dots in active region for photon absorption in the long-wavelength part of spectrum and increase in the efficiency of the conversion of solar energy in electrical power is carried out. Problems of theory and experiment of low-dimensional solar cells (quantum well and quantum dot solar cells) are discussed.
The impedance and noise characteristics of a semiconductor punch-through structure are theoretically examined for an operation under a condition when quantum wells (QWs) are present in the transit-time region of the structure. It is shown that the magnitude of the negative dynamic resistance can be increased under the influence of the trapping and escape effects of injected carriers by quantum wells. It is expected that the structure proposed have significantly higher operation frequencies in comparison with usual barrier-injection transit-time diode. It is shown also that the noise measure decreased under an influence injected charge carriers captured by QWs with the increase of the ration of the emission time of electrons emitted out of QWs due to the thermal excitation to the capture time of free charge carriers. The frequency band where this phenomenon takes place is narrowed and displaced to a lower frequency range.