Polarization Doped Nanowire Devices as an Alternative to Impurity Doping

Abstract

It is difficult to control electrical conductivity in wide band gap semiconductors using impurity doping because of large ionization energies in these materials. Polarization-induced doping in compositionally graded heterostructures is a possible alternative to impurity doping in certain wide band gap materials. Here we present compositionally graded AlGaN nanowires grown on Si(111) substrates by plasma-assisted molecular beam epitaxy that utilize polarization-induced doping to form p-n junctions. GaN quantum wells are inserted into the nanowires to create polarization-induced nanowire light emitting diodes (PINLEDs) that emit ultraviolet light. Variable temperature electrical measurements show that dopants in the structure are ionized by polarization-induced charge and therefore do not freeze-out at cryogenic temperatures. Furthermore, electroluminescence measurements show that polarization-induced charge alone (i.e. with no intentionally added dopants) can be used to form working LEDs.