Mechanism for increasing dopant incorporation in semiconductors via doped nanostructures

A long-standing problem for ZnSe (and related alloys) has been to obtain good p-type doping. Recent work has given about an order-of-magnitude improvement in such doping by use of Te as a "codopant" to facilitate the introduction of an acceptor dopant (N), since it is known that p-ZnTe can be obtained quite readily; the Te was introduced in submonolayer quantities via planar (delta) doping during molecular beam epitaxy. Here, we examine the mechanism of this improved doping. We show that it resides in the formation of ZnTe-rich nanoislands, with the N embedded in these. This result is obtained by studies involving transmission electron microscopy, high-resolution x-ray diffraction, secondary-ion mass spectroscopy, and temperature quenching of photoluminescence. We note that these nanoislands appear quite unique, in providing doping of semiconductors, and thus are of great interest of their own.