CHARGE CONTROL MODEL OF THE DOUBLE DELTA-DOPED QUANTUM-WELL FIELD-EFFECT TRANSISTOR

The charge control properties of Al0.3Ga0.7As-GaAs-Al0.3Ga0.7As quantum-well field-effect transistor (FET) with double delta-doped planes are studied theoretically. A simple capacitor-like charge control model for the double- delta-doped quantum-well FET's has been proposed and verified through self-consistent calculation. The threshold voltage and the capacitance can be related to the structure through simple analytical equations. The effective separation between capacitor plates is found to be the thickness of AlGaAs layer d + d(i) + delta plus a correction term to account for the distribution of N2DEG inside the GaAs quantum well. For small well widths, only the ground-state subband is occupied and there is a simple linear relation between N2DEG and the gate bias V(G). For larger well widths, electrons occupied the lowest subband, then the next higher energy subband, and the relation between the N2DEG and the V(G) can be divided into piece-wise linear regions.