Tunneling peculiarities in asymmetrical quantum-well structures

Asymmetrical quantum-well structures (AMQW) are layered semiconductor heterostructures having quantum wells of various depth, width, and shape. There are dimensional, compositional, and compound AMQW depending on the cause, which defines potential profile. In SOA with multiple quantum-wells and AMQW as well as in quantum-well lasers carrier transport effects become important and govern nonuniform carrier distribution along the active area. As a rule tunneling transfer is neglected under simulation of multiple quantum-well dynamics. However, tunneling can make significant concurrence for other transport processes under room temperature and thin barriers. The tunneling is the transfer of charge carriers between wells without variation of their energy. Since the structure under consideration is multilayered quantum wells this kind of carrier transfer provides resonant behavior. To take tunneling into account in the frame of rate equations we describe the tunneling rate by means tunneling time. For tunneling time computation we use the group velocity conception in the frame of semiclassical treatment. Our simulations have showed that tunneling time can be comparable to other transport times and even less.