Mn doping and p-type conductivity in zinc-blende GaMnN layers grown by molecular beam epitaxy

Abstract

Mn-doped cubic GaN films were grown by plasma-assisted molecular beam epitaxy on GaAs (001) substrates. There was a strong influence of the Ga:N ratio on the Mn incorporation and a dramatic increase in the Mn concentration was observed for the layers grown under N-rich conditions. Hall-effect measurements unambiguously showed that the GaMnN samples had strong p-type conductivity. For both N-rich and Ga-rich growth conditions a bulk hole density of about 1018cm−3 was achieved with a corresponding mobility of >300cm2V−1s−1. This compares very favorably with other values reported for p doping of cubic GaN doped with C, suggesting that Mn may be a very suitable dopant for GaN-based electronic structures. The apparent values of ionization energy for Mn were around 50 meV, which is much shallower than for C or Mg in cubic GaN. In addition to a small high temperature ferromagnetic signal, a ferromagnetic correlation was detected among the remaining Mn ions at low temperatures, which is assigned to the onset of hole-mediated ferromagnetism in cubic GaMnN.

Structural characterisation of zinc-blende Ga1−xMnxN epilayers grown by MBE as a function of Ga flux

“…The sample magnetic properties were investigated using a superconducting quantum interference device magnetometer with the magnetic field applied in the sample plane. The samples grown under N-rich conditions (samples A-D) and slightly Ga-rich conditions (sample E) exhibited a ferromagnetic signal above 400 K [6] attributable to a second-phase material, with relative signal strength as summarised in Table 1, while room temperature ferromagnetism was suppressed for samples grown under higher Ga-rich conditions.…”

“…The electrical properties of these samples were appraised in detail as published elsewhere [6,24]. Briefly, a hole concentration of 410 18 cm À3 with a corresponding mobility of 4300 cm 2 /Vs was achieved, with a drop in hole mobility for samples grown under increasing Ga-rich conditions.…”

“…In practice, establishing p-type conductivity is found comparatively easier within zinc-blende Ga 1Àx Mn x N than wurtzite Ga 1Àx Mn x N, where the transition metal species needs to be responsible for both the ferromagnetic properties and the p-type behaviour. By way of example, high p-type zinc-blende Ga 1Àx Mn x N layers with carrier concentrations exceeding 10 18 cm À3 and a detected ferromagnetic signal over 400 K have been obtained by PAMBE [4][5][6]. Room temperature ferromagnetism and ptype conductivity have also been reported for PAMBE grown zinc-blende GaN following Mn + ion implantation and annealing [7].…”

MBE growth of GaN using 15N isotope for nuclear magnetic resonance applications

“…An additional arsenic flux was used to initiate the growth of the zinc-blende phase of GaN, as previously described in details elsewhere [4]. In the majority of structures, before the growth of GaN layers, a GaAs buffer layer was grown on the substrate in order to improve the quality of GaN films.…”

Nanoscale Characterisation of MBE-Grown GaMnN/(001) GaAs

“…However, the low solid solubility of Mn in GaN limits the development of these systems. T c values exceeding room temperature have been reported for (Ga,Mn)N, although the source of the ferromagnetic signal has not been definitively identified [4,5]. The requirement for p-type (Ga,Mn)N material is most practically achieved by growing the cubic phase using plasma assisted MBE (PAMBE) on (001)GaAs [2].…”