Characterization of multiple carriers in GaN using variable magnetic-field hall measurements

Abstract

Variable magnetic-field Hall-effect measurements were performed on two thick GaN samples grown by hydride vapor-phase epitaxy (HVPE), one freestanding and one attached to the sapphire substrate. Results are compared to those obtained using the more standard, single magnetic-field Hall measurements. In both samples, a second low-mobility electron was indicated that significantly influenced interpretation of single-field Hall measurements, particularly at low temperatures. Extraction of the bulk carrier using fits to the variable-field Hall data allowed a more accurate determination of the temperature dependence of the bulk electrical properties and, hence, basic physical parameters. In addition, the quantitative mobility-spectrum analysis (QMSA) technique, reported here for the first time on GaN, indicated a continuous and significant spread in mobility for the bulk electron, likely with sample thickness. Thus, even the "improved" results, based on modeling the multiple-carrier fitting (MCF) analysis, obtained in this study should be viewed with some suspicion, as they clearly represent an average over an electrically inhomogeneous sample.

Growth parameter investigation of Al0.25Ga0.75N/GaN/AlN heterostructures with Hall effect measurements

“…There is a small contribution from thermally activated high mobility carriers to the measured carrier density at high temperatures. The origin of the high mobility is not clear, but the results are consistent with the high bulk mobility values of 4000-10000 cm 2 V −1 s −1 for GaN, which is suggested by Swartz et al [35]. At low temperatures, the extracted 2DEG Sheet Carrier Density (cm -2 ) mobility is slightly higher than the measured mobility.…”

MBE growth and characterization of Mn-doped InN

“…In order to resolve the distinct carrier populations when multiple carriers are present, either the conductivity of the low mobility species must be dominant or the condition of (lB) 2 > 1 needs to be met, where l is the mobility and B is the magnetic field. 14 The broad distribution in hole mobility is attributed to inhomogeneity in the film, 18 which is not unexpected for InN films grown under N-rich conditions. The measured conductivity tensors can be analyzed using either quantitative mobility spectrum analysis (QMSA) or multiple carrier fitting (MCF).…”

Self-consistent scattering analysis of Al0.2Ga0.8N/AlN/GaN/AlN heterostructures grown on 6H-SiC substrates using photo-Hall effect measurements

“…QMSA can extract the mobilities and sheet carrier densities of each species or conduction mechanisms by analyzing the magnetic field dependent Hall measurement data [13]. The QMSA technique has been applied successfully to various systems, including bulk InN [14], GaN epilayers [15], and AlGaN/GaN heterostructures [16]. However, the dimensionless product of lowest mobility and the highest field must be greater than unity to clearly identify additional carriers (μ min B max 1).…”