Dependence of the Mn sticking coefficient on Ga-rich, N-rich, and Ga/N-flux-free conditions in GaN grown by plasma-assisted molecular beam epitaxy

TL;DR

This work investigates how Ga/N flux conditions during plasma-assisted MBE growth affect Mn incorporation in GaN. Using a GaN:Mn/GaN multilayer, Mn incorporation is quantified under Ga-rich, N-rich, and no-flux (δ-doping) conditions, with Mn sticking coefficients normalized to the N-rich case. The highest Mn density occurs under N-rich growth (~$1e20$ cm$^{-3}$), while Ga-rich growth yields ~$1e18$ cm$^{-3}$ and no-flux δ-doping yields ~$1e19$ cm$^{-3}$, corresponding to Mn sticking coefficients of ~0.01 and 0.31, respectively, relative to N-rich. The results demonstrate that the growth regime predominantly controls Mn incorporation, with implications for Mn-doping strategies in GaN and parallels to Mg doping behavior.

Abstract

This brief report examines the influence of Ga/N flux conditions on Mn incorporation in GaN. Mn-doped GaN layers were grown at 680$^{\circ}$C by molecular beam epitaxy on a Ga-polar GaN(0001) template substrate under Ga-rich, N-rich, and no-flux conditions (i.e., Mn $δ$ doping). Mn incorporation was highest under N-rich condition, lowest under Ga-rich condition, and intermediate in the absence of Ga and N fluxes. For the growth conditions examined in this study, the corresponding Mn sticking coefficients, relative to that of the N-rich condition, were determined to be 0.31 for no-flux growth and 0.01 for the Ga-rich growth.

Figures (2)

• Figure 1: (a) Schematic layer structure of GaN:Mn/GaN multilayers grown on a GaN template at 680$^{\circ}$C by MBE. The double and single asterisks indicate growth interruptions of 12 min. and 6 min., respectively. (i)--(v) RHEED patterns taken along the $<$11$\bar{2}$0$>$ azimuth at various stages of the growth, as indicated by the lines connected to (a). The two yellow arrows in (v) highlight the diffraction patterns associated with a contracted Ga bilayer on the GaN surface. [(b), (c)] AFM micrographs of the Mn-doped GaN multilayer structure, showing (b) the as-grown surface and (c) a sputtered substrate region after SIMS measurements. The RMS roughness over a $2\times2$$\mu$m$^{2}$ area is 0.68 nm for (b) and 0.64 nm for (c).
• Figure 2: SIMS depth profiles of GaN:Mn/GaN multilayers grown on a GaN template at 680$^{\circ}$C by MBE, showing (a) O, C, Si, and H and (b) Mn concentrations in the layers, with detection limits of $3\times10^{15}$ cm$^{-3}$ for Si and O, $1.5\times10^{15}$ cm$^{-3}$ for C, $1\times10^{17}$ cm$^{-3}$ for H, and $1\times10^{15}$ cm$^{-3}$ for Mn.