The quasibound state model for self-consistent characteristics of semiconductor intersubband devices

The quasibound state model (QBSM) for determining the self-consistent condu ction band profile and space charge density of semiconductor intersubband d evices is presented. This new method is based on the quasibound (QB) state resonances of quantum structures. For heterostructures, the traditional sel f-consistent energy continuum model (ECM) calculates space charge by integr ation over the entire energy continuum, weighted by Fermi-Dirac statistics. In the present approach, the continuum of energy states of the heterostruc ture is accurately represented by a small number of QB states, and the spac e charge calculations are performed only at these eigen-energies. This appr oach significantly reduces the computational burden associated with all sel f-consistent algorithms. Theoretical formulation of QBSM is compared with t he traditional ECM approach. The bound (B) and QB eigenenergies of the stru cture are obtained by solving the single-band effective-mass Schrodinger eq uation using the argument principle method. The performance and the accurac y of the QBSM are evaluated for a double-barrier resonant structure and an asymmetric Fabry-Perot electron-wave interference filter. The self-consiste nt electron density and potential profiles calculated by the present method are shown to be in excellent agreement with the results obtained from the traditional ECM model. In addition to requiring less computational time, th e present method is easily implemented and may be applied equally well to b iased/unbiased, symmetric/asymmetric heterostructures. (C) 2001 Academic Pr ess.