Modeling the Energy Structure of a GaN p–i–n Junction

Abstract

The second-order differential equation, which includes the density distribution function of a mobile charge in a compensated layer of the GaN diode p–i–n junction is derived. The equation is solved numerically using the MathCad software. The electric field at the interface between the doped and compensated layers is calculated under the assumption of the concentration of electrons diffused into the compensated layer being much higher than the concentration of the immobile compensated impurity ions. Electrons from the heavily doped layer diffuse into the compensated layer and leave positively charged donor impurity ions there. The electric field ε induced between the layers of mobile electrons and ions compensates the diffusion flow by the drift flow. The charged layers of mobile carriers screen the external electric field. Based on the solution of the differential equation, diagrams of the electric field and potential distribution in the GaN p–i–n junction’s space charge region (SCR) are built taking into account the effect of free carriers. It is shown that in the nonexponential portion of the I–V characteristic, the drift field is induced in the compensated layer, which limits the growth of the forward current.