Comprehensive magnetotransport characterization of two dimensional electron gas in AlGaN/GaN high electron mobility transistor structures leading to the assessment of interface roughness

Abstract

Magnetotransport in two distinct AlGaN/GaN HEMT structures grown by Molecular Beam Epitaxy (MBE) on Fe-doped templates is investigated using Shubnikov de-Haas Oscillations in the temperature range of 1.8–6 K and multicarrier fitting in the temperature range of 1.8–300 K. The temperature dependence of the two dimensional electron gas mobility is extracted from simultaneous multicarrier fitting of transverse and longitudinal resistivity as a function of magnetic field and the data is utilized to estimate contribution of interface roughness to the mobility and the corresponding transport lifetime. The quantum scattering time obtained from the analysis of Shubnikov de Haas Oscillations in transverse magnetoresistance along with the transport lifetime time were used to estimate interface roughness amplitude and lateral correlation length. The results indicate that the insertion of AlN over layer deposited prior to the growth of GaN base layer on Fe doped GaN templates for forming HEMT structures reduced the parallel conduction but resulted in an increase in interface roughness.

A Low-Power Microwave HEMT $LC$ Oscillator Operating Down to 1.4 K

“…This value for the density of carriers is in good agreement with the above-estimated one, obtained from the measurements of the resistance (i.e., 5 × 10 16 m −2 ). The SdH oscillations reported in this paper are significantly smaller than those reported in previous publications [64]- [68]. This might be due to the larger electric fields applied to the HEMT transistor with respect to those usually reported in the literature.…”

“…Since the conductivity is defined as σ = enμ (where e is the elementary charge, n is the density of carriers, and μ is the mobility) and the resistance is R DS = L SD /W σ (where L SD = 2.5 μm and W = 60 μm are the transistor source-drain distance and width, respectively), we estimate a density of carriers of about 5 × 10 16 m −2 . In order to cross-check such a result, we measured the periodicity of the SdH oscillations [60], [64]. In our case, the SdH oscillations are the oscillations of R DS as a function of the applied magnetic field, which we measured at 1.4 K. As shown in Fig.…”

“…3(e) and (f) there is a main frequency component at about 70 T −1 . According to [64], we compute the density of carriers as n ∼ = (2e/ h/(1/B)) ∼ = 3.5 × 10 16 m −2 , where h is the Planck constant and (1/B) is the periodicity of the SdH oscillations. This value for the density of carriers is in good agreement with the above-estimated one, obtained from the measurements of the resistance (i.e., 5 × 10 16 m −2 ).…”

k-space imaging of anisotropic 2D electron gas in GaN/GaAlN high-electron-mobility transistor heterostructures

“…In our case, the QWS 2 contributes only ~ 4% of the total n s dominated by the QWS 1 . A significant difference of this ratio to that of 17% found in a cyclotron resonance study 28 is explained by extremely high sensitivity of the QWS 2 population to the interfacial QW depth in different samples. The total n s in our case amounts to (13.3 ± 1.8) × 10 12 cm −2 , which is in fair agreement with n s = 8.2 × 10 12 cm −2 obtained by our Hall characterization, see Fig.…”

Growth and Characterization of Nitrogen‐Polar AlGaN/AlN Heterostructure for High‐Electron‐Mobility Transistor

“…To solve this problem, we suggest N‐polar (Al) GaN/AlN and simulate its device performance using the field‐effect transistor‐integrated simulator (FETIS) software . In a N‐polar (Al) GaN/AlN structure, a 2DEG can be generated at the heterointerface by the coherent growth of (Al) GaN on N‐polar AlN . When the AlN underlayer is adopted, very high resistivity leads to the realization of a high breakdown voltage, due to its wide bandgap.…”