Current Induced Potential Well in Compensated Semiconductors

To obtain high resistivity samples in the case of III‐V compounds such as GaAs or InP, deep levels are often used as compensating centers for residual shallow dopants. These levels usually have very different capture cross sections for electrons (σn) and holes (σp). We consider here a GaAs P+‐semi‐insulating (SI)‐N+ structure whose SI central zone consists of two layers of equal thickness. One layer is made with an electron trap as the compensating level (σn ≫ σp; τn, t ≪ τp, t), the other layer is made with a hole trap as the compensating level (σp ≫ σn; τp, t ≪ τn, t). Numerical simulations under forward bias show that electron and hole injection across the contacts induce, at the interface between the two layers, a space charge region as in a P‐N junction. The resulting potential barrier can either assist or oppose the current, depending on the nature of the compensated layer (electron trap or hole trap) adjacent to the injecting contact. We also present here numerical results for a three‐layer structure. For this structure, a potential well develops across the middle layer under forward bias conditions.