Rare Earth Doped GaN Laser Structures Using Metal Modulated Epitaxy.

摘要

A new growth scheme named Phase Shift Epitaxy (PSE) was developed. PSE is a periodic and dynamic growth scheme, which desynchronizes the host material growth with dopant incorporation by adjusting delays between shutters operation, frees the doping condition from limited host material growth condition confined by stoichiometry. PSE takes advantage of various surface conditions during each cycle. The overall uncompromised host quality and dopant can be introduced strategically at desired surface condition. This technique is first applied to Eu doping of GaN. Doping Eu in Ga rich condition leads to 10x enhancement of the photoluminescence efficiency of Eu ions at a specific peak (620 nm) and 50% enhancement of the overall PL efficiency compared with optimum traditional MBE condition. PSE is also used for Mg doping of GaN to achieve p-type conductivity. Mg self-compensation effect is postponed to higher Mg concentration when Mg is doped in N rich condition and thus high hole concentration (2.4E18cm-3) is achieved. The highest Mg concentration by PSE is comparable to the highest concentration ever published thanks to the suppression of self-compensation effect. Phase Shift Epitaxy is thus proved effective in doping of GaN. PSE grown active layer (GaN:Eu) and p-type layer are tested in devices such as GaN p-n junction and GaN:Eu LED.