Possible terahertz laser structures based on population inversion induced by resonant states in semiconductors

We theoretically examine the possible InGaAs/GaAs and SiGe/Si QW structures that may fulfill the criterion to achieve a terahertz (THz) laser device a ccording to the new mechanism of unipolar-type population inversion discuss ed in the recent letter (Phys. Rev. Lett. 83 (1999) 644. Our calculations a re based on well-developed effective-mass theory that accounts for valence- hand mixing as well as the mismatch of band parameters and dielectric const ants between well and barrier materials. The advantage of the model is that the ground and excited states of accepters confined in strained quantum we ll structures can be calculated. Therefore, by calculating the splitting of the acceptor ground states in strained InxGa1-xAs/GaAs and Si1-xGex/Si qua ntum well structures versus well widths and alloy concentrations, our resul ts provide a guiding to design the structures that may be suitable for real izing THz stimulated emissions in a range between 2.5 and 7.5 THz, which co rresponds to an energy range between 10 and 30 meV. (C) 2000 Elsevier Scien ce B.V. All rights reserved.