Abstract
The electron transport lifetime τ in low-dimensional semiconductor devices
based on quantum well structures is an important parameter that decides the transport
as well as optical properties. In recent times, the utilization of non-square quantum well
structures has boosted the optoelectronic device performance. This chapter reports the
variation of τ with the applied electric field Fapp in Alx Ga1-x As-based modulation doped
double quantum well (DQW) structures by considering non-square potential profiles
such as parabolic (P), V-shaped (V), semi-parabolic (SP), and semi-V-shaped (SV).
Here, τ is analyzed by adopting ionized impurity (imp) and alloy disorder (al)
scatterings. In the case of DPQW and DVQW systems, two subbands are occupied
from Fapp = 0 up to |Fapp| = 5.6 kV/cm. After that, only one subband is occupied. On the
other hand, in the case of DSPQW and DSVQW, there occurs the occupation of only a
single lowest subband energy level for all Fapp. It is significant to note that the effect of
the scattering mechanism on the subband transport lifetime differs by changing the
structure potential. For example, when both lower and upper subbands are filled, in the
case of DPQW, the imp-scattering decides τ, whereas, in the case of DVQW, both impand al-scatterings equally contribute. The results of τ in the structures given below are
compared with the conventional double square quantum well (DSQW) structure and
show that τ (DPQW) > τ (DVQW) > τ (DSQW) at Fapp = 0. The results of τ in nonsquare DQW structures will be very helpful in understanding the intricacies of the
electro-optical properties of emerging low-dimensional semiconductor devices.