Two-dimensional electron and hole gases in InxGa1−xN/AlyGa1−yN/GaN heterostructure for enhancement mode operation

In this paper, a numerical study of In x Ga1 − x N/Al y Ga1 − y N/GaN heterostructure is presented. The dependence of two-dimensional electron gas (2DEG) and two-dimensional hole gas (2DHG) sheet densities on variables, such as In x Ga1 − x N layer thickness and In content, and Al y Ga1 − y N barrier layer thickness and Al content, are systematically investigated. The effect of P-type doping in In x Ga1 − x N on 2DEG and 2DHG sheet densities in this heterostructure is also studied. It is shown that the strong reverse electric field in In x Ga1 − x N cap layer contributes to the depletion of 2DEG at the Al y Ga1- y N/GaN interface. When In x Ga1 − x N layer thickness and In content increases, 2DEG sheet density decreases significantly. P-type doping shows less influence on 2DEG compared to the polarization electric field in In x Ga1 − x N layer. In addition, there exist critical values for all the variables beyond which 2DHG appears at the interface of In x Ga1 − x N/Al y Ga1 − y N. Once 2DHG appears, it will prevent 2DEG from being further depleted. With proper design of Al y Ga1 − y N layer, the coexistence of 2DEG and 2DHG in In x Ga1 − x N/Al y Ga1 − y N/GaN structure can be avoided, showing that this structure has great potential in the fabrication of enhancement mode (E-mode) high electron mobility transistors.