Effect of Graded Base p-Doping on MIM Performance.

0.6 eV InGaAs/InPAs double heterostructure n/p/n tunnel junction monolithic interconnected modules (TJ-MIMs) having p-type bases doped uniformly at 2×10[sup 17] cm[sup -3] and inhomogeneously graded from 4 × 10[sup 16] cm[sup -3] to 4 × 10[sup 17] cm[sup -3] (10:1 doping ratio) were grown, processed, and characterized. The electrical performance of the devices with inhomogeneously graded bases was higher than that of the uniformly doped case due to the built-in electric field in the base region, making QE[sub int] and J[sub SC] larger. The free carrier absorption increased due to the relatively higher doping levels for the linearly doped case but remained unchanged for the exponential profile. Therefore, results showed that exponentially grading the base p-type doping increased the MIM performance by ∼ 8% (relative). [ABSTRACT FROM AUTHOR]