Electrical characteristics of vertical-geometry Schottky junction to magnetic insulator (Ga,Mn)N heteroepitaxially grown on sapphire

Abstract

Schottky barrier height and the ideality factor  are established for the first time in the single phase (Ga,Mn)N using a vertical geometry device. The material has been heteroepitaxially grown on commercially available low threading dislocation density GaN:Si template. The observed above 10 M resistances already at room temperature are indicative that a nearly conductive-dislocation-free electrical properties are achieved. The analysis of temperature dependence of the forward bias I-V characteristics in the frame of the thermionic emission model yields Ti-(Ga,Mn)N Schottky barrier height to be slightly lower but close in character to other metal/GaN junctions. However, the large magnitudes of the ideality factor  > 1.5 for T  300 K, point to a sizable current blocking in the structure. While it remains to be seen whether it is due to the presence of (Ga,Mn)N barrier or due to other factors which reduce the effective area of the junction, an existence of a substantial serial resistance may hold the key to explain similar observations in other devices of a corresponding structure and technological relevance.

Raman scattering studies of the lateral Mn distribution in MBE-grown Ga1-Mn N epilayers

“…The main feature provided by this plot is that  LO decreases with x, a fact anticipated on the account of the increase of the c lattice parameter on x in (Ga,Mn)N epilayers [5][23]. This assumption is fully corroborated by the insulating character of magnetically homogeneous (Ga,Mn)N bulk crystals [47] and epilayers [28,[48][49][50], thus no influence of phonon-plasmon coupling is expected here. Now, guided by the spread of the points in Fig.…”

“…Because of the strong sensitivity of T C on x (T C ~ x 2.2 ) [22], as in other superexchange-coupled dilute magnetic semiconductors (DMS) [24][25][26][27], the lateral distribution of x in homogeneous Ga 1−x Mn x N layers can be quite precisely tracked by magnetic measurements [5]. Both the rather low magnitudes of T C (below about 13 K) and the highest magnetic saturations among all Mn-containing DMS compounds allow a relatively accurate assessment of x, and, as argued recently [28], these features are strongly indicative of a prevalence of Mn in +3 oxidation state. Magnetometry is, generally, a time consuming and, most predominantly, a destructive characterization method, since the original, the as grown material has to be fragmented into small pieces to fit into the sample chamber of the magnetometer.…”

Improved-Sensitivity Integral SQUID Magnetometry of (Ga,Mn)N Thin Films in Proximity to Mg-doped GaN

“…Therefore, on the account of the accumulated body of evidences in the low to medium doped (Ga,Mn)N, i.e. for x not greater than several % [23,25,36,38,39], the combined data presented in Fig. 3 constitute the telltale evidence of the prevalence of the Mn 3+ state of Mn ions in the (Ga,Mn)N layer.…”

“…In the low temperature regime, the FM obeys a clear phase diagram and is so robust that the critical exponents for the paramagnetic-ferromagnetic phase transitions were experimentally determined [23]. These layers are devoid of carriers [24,25] and the Fermi level is pinned on the only partially filled Mn 3+ level in the mid-gap region of GaN [26][27][28]. In the absence of carriers, the necessary Mn-Mn coupling is provided by superexchange.…”