Band-Gap Engineering for New Photonic and Electronic Devices

Interface roughness and asymmetric current-voltage characteristics in resonant tunnelling

“…When calculating the square of the matrix element in equation (3) we take the mean value of the product h(R)h(R') and use equation ( 1) before making the integration.…”

“…Vis the volume and V = L,A ( A is the area, and L , is the length in the perpendicular direction). The rate from equation (3) can now be calculated, using equations ( 1) and ( 4), to give:…”

“…This leads to a peak in the current-voltage ( I -V ) characteristics: as the applied voltage is increased the current reaches a maximum after which it decreases in a region of negative differential resistance (NDR). Devices based on doublebarrier structures can be used for a number of applications, for instance for fast electronic switches [3], for the generation of microwave oscillations [4] or as a frequency multiplier for very high frequencies [S].…”

Tunneling Behaviors of Photogenerated Electrons in In0.15Ga0.85As/GaAs Quantum Well Photoelectrodes

“…Quantum wells (QWs) and superlattices (SLs) have drawn much attention in semiconductor physics research and semiconductor-based device development due to their unusual physical properties arising from the energy quantizations and engineered electronic structures. , A multiple quantum well (MQW) semiconductor used in a solar cell has proved to be in possession of higher conversion efficiency than a bulk semiconductor in the lattice-matched GaAs/(AlGa)As system. − Nozik et al first introduced the superlattice and quantum well electrodes as new kinds of semiconductor photoelectrodes into photoelectrochemical studies. − They studied the quantum confined effect of photoelectrodes and hot electron transfer at a p-doped strained layer or lattice-matched SLs/electrolyte interface, which can dramatically improve the conversion efficiency of the semiconductor photovoltaic cell . Recently, using the tailored band structure of QW, the thermodynamic and dynamic characteristics at the surface of QW electrodes were extensively investigated.…”

Optical phonons in resonant tunnelling

“…The NDR can be used for generating microwaves [3] of very high frequencies. There is also a possibility for a new generation of computer switches that would operate at a much larger speed than the traditional ones [4]. For good performance in both cases the so-called peak-tovalley ratio has to be as large as possible, this is defined as the ratio between the peak current before the NDR and the valley current directly after.…”