We investigate new schemes of M-based heterostructure barrier varactor
s with the aim of enhancing the capacitance nonlinearity of the device
s. Starting from a generic steplike InGaAs/LnAlAs/AlAs single barrier
heterostructure, planar-doped and buried InAs quantum-well barrier het
erostructures were successfully fabricated. It is shown that both solu
tions lead to more efficient screening of electric held near equilibri
um and hence to improvement in the capacitance-voltage ratios with val
ues as high as similar to 7:1. Under bias, the capacitance modulation
is governed by an escaping mechanism in contrast to the conventional d
epletion operation mode observed for conventional varactors.