Modeling the effects of surface potential on gallium nitride betavoltaic cell collection efficiency

The surface potential of P-type Gallium Nitride (GaN) is modeled using a Metal-Oxide-Semiconductor (MOS) based field plate. Using this model, the charge collection efficiency of a PN junction GaN betavoltaic device was simulated. By including the effects of incomplete ionization together with the surface potential, the P-layer’s thickness design can be optimized. The model indicates for P-type doping of 1 × 10 19 cm -3 , 87% of the zero-surface barrier collection efficiency can be obtained. However, if only 1 × 10 18 cm -3 doping can be achieved, the collection efficiency will be only 57% of the maximum zero-surface barrier collection. As a result, heavily doped, ultra-thin P-layers enable improved carrier collection and higher efficiency under elevated surface potential conditions.