Electrical injection in longitudinal and coaxial heterostructure nanowires: a comparative study through a three-dimensional simulation.

We carried out a comparative study of electrical injection in longitudinal p-i-n and coaxial p-n core-shell nanowires by performing a three-dimensional numerical simulation. In the case of the core-shell structure, we show that both electrons and holes of high density can be efficiently injected into and confined in the structure even without an i-region. The required bias voltage and doping concentrations in the core-shell structure are smaller than those in the longitudinal p-i-n structure to achieve the same carrier injection level. Furthermore, we show that a type-I band alignment, as required in traditional p-i-n structure is not necessary in core-shell structure, allowing more flexibility in nanowire devices design. Our results thus provide a theoretical foundation and understanding that a core-shell structure is far superior to the longitudinal p-i-n structure for electrical injection nanowire lasers.