Abstract:We report evidence of the transition from n- to p-type conduction of InN with increasing Mg dopant concentration by using photoconductivity (PC) measurement at room temperature. This transition is depicted as a conversion from negative to positive PC under above-bandgap optical excitation. The n- to p-type transition in InN:Mg is further confirmed by thermopower measurements. PC detection method is a bulk effect since the optical absorption of the surface electron accumulation is negligibly low due to its rath… Show more
“…This could be explained by the Mg doping position changing from the interstitial sites to the substitutional In-sites, forming In 1- x Mg x N alloys as the Mg source temperature increased. This result is in agreement with Wang’s results that with the increase of the Mg cell temperature, InN was firstly n type being slightly Mg doped, then became p type with enough Mg acceptors higher than ionized donors, and finally became n type again because of over-doped Mg [ 7 – 10 ]. Fig.…”
Section: Resultssupporting
confidence: 92%
“…In recent years, high-quality InN films have been grown by molecular beam epitaxy (MBE) [ 5 , 6 ]. Although the surface electron accumulation is not completely explained and solved, p-type carriers have been confirmed in Mg-doped InN by indirect evidences such as measurements of electrolyte-based capacitance-voltage (ECV) [ 7 ], temperature-dependent Hall effect [ 8 ], thermopower [ 9 ], and photoconductivity [ 10 ]. All efforts mentioned above lay a good foundation for the fabrication of high-quality Mg-doped InN MISFETs and MIS-HEMTs.…”
InN-based metal-insulator-semiconductor (MIS) structures were prepared with Al2O3 as the gate oxides. Surface morphologies of InN films are improved with increasing Mg doping concentrations. At high frequencies, the measured capacitance densities deviate from the real ones with turning frequencies inversely proportional to series resistances. An ultralow leakage current density of 1.35 × 10−9 A/cm2 at 1 V is obtained. Fowler-Nordheim tunneling is the main mechanism of the leakage current at high fields, while Schottky emission dominates at low fields. Capacitance densities shift with different biases, indicating that the InN-based MIS structures can serve as potential candidates for MIS field-effect transistors.
“…This could be explained by the Mg doping position changing from the interstitial sites to the substitutional In-sites, forming In 1- x Mg x N alloys as the Mg source temperature increased. This result is in agreement with Wang’s results that with the increase of the Mg cell temperature, InN was firstly n type being slightly Mg doped, then became p type with enough Mg acceptors higher than ionized donors, and finally became n type again because of over-doped Mg [ 7 – 10 ]. Fig.…”
Section: Resultssupporting
confidence: 92%
“…In recent years, high-quality InN films have been grown by molecular beam epitaxy (MBE) [ 5 , 6 ]. Although the surface electron accumulation is not completely explained and solved, p-type carriers have been confirmed in Mg-doped InN by indirect evidences such as measurements of electrolyte-based capacitance-voltage (ECV) [ 7 ], temperature-dependent Hall effect [ 8 ], thermopower [ 9 ], and photoconductivity [ 10 ]. All efforts mentioned above lay a good foundation for the fabrication of high-quality Mg-doped InN MISFETs and MIS-HEMTs.…”
InN-based metal-insulator-semiconductor (MIS) structures were prepared with Al2O3 as the gate oxides. Surface morphologies of InN films are improved with increasing Mg doping concentrations. At high frequencies, the measured capacitance densities deviate from the real ones with turning frequencies inversely proportional to series resistances. An ultralow leakage current density of 1.35 × 10−9 A/cm2 at 1 V is obtained. Fowler-Nordheim tunneling is the main mechanism of the leakage current at high fields, while Schottky emission dominates at low fields. Capacitance densities shift with different biases, indicating that the InN-based MIS structures can serve as potential candidates for MIS field-effect transistors.
“…The response of samples with different Mg cell temperatures and different gas atmospheres were shown in Figure 6 a. According to previous reports and the sample growth conditions [ 31 , 32 , 33 , 34 , 35 ], there are three regions with increasing Mg cell temperature (T Mg ): Region I (T Mg < 220 °C) and III (T Mg > 260 °C) refers to the slightly-doped and overdoped regime, where the samples are n-type. Region II (220 °C < T Mg < 260 °C) usually shows the evidence of p-type conduction in the bulk.…”
Section: Resultsmentioning
confidence: 68%
“…We assume that the influence of proximity between these two layers could be negligible and they are shorted at the contacts [ 32 , 36 ]. The relationship for the multilayer model is [ 27 , 31 ]: where σ total is the total sheet conductivity; n and μ are carrier density and carrier mobility, respectively; the subscript s and b represent the surface electron accumulation layer and the bulk, respectively; d represents the thickness of bulk; and H represents the direct measurement value.…”
It is a fact that surface electron accumulation layer with sheet electron density in the magnitude of ~1013 cm−2 on InN, either as-grown or Mg-doped, makes InN an excellent candidate for sensing application. In this paper, the response of hydrogen sensors based on Mg-doped InN films (InN:Mg) grown by molecular beam epitaxy has been investigated. The sensor exhibits a resistance variation ratio of 16.8% with response/recovery times of less than 2 min under exposure to 2000 ppm H2/air at 125 °C, which is 60% higher in the magnitude of response than the one based on the as-grown InN film. Hall-effect measurement shows that the InN:Mg with suitable Mg doping level exhibits larger sheet resistance, which accords with buried p-type conduction in the InN bulk. This work shows the advantage of InN:Mg and signifies its potential for sensing application.
“…Finally, a 70 nm thick layer of undoped InN and a 10 nm thick barrier layer of InGaN were grown at 500 °C with a 96% In composition. The Mg cell temperature was kept at 250 °C during the growth of the Mg‐doped InN to create a p‐type conductive material, which should reduce the contribution of the undoped InN layer to the conductivity of the total heterostructure 29. Atomic force microscopy (AFM) measurements revealed an atomically flat surface with step terraces, as shown in Figure 1b.…”
Due to the intrinsic spontaneous and piezoelectric polarization effect, III‐nitride semiconductor heterostructures are promising candidates for generating 2D electron gas (2DEG) system. Among III‐nitrides, InN is predicted to be the best conductive‐channel material because its electrons have the smallest effective mass and it exhibits large band offsets at the heterointerface of GaN/InN or AlN/InN. Until now, that prediction has remained theoretical, due to a giant gap between the optimal growth windows of InN and GaN, and the difficult epitaxial growth of InN in general. The experimental realization of 2DEG at an InGaN/InN heterointerface grown by molecular beam epitaxy is reported here. The directly probed electron mobility and the sheet electron density of the InGaN/InN heterostructure are determined by Hall‐effect measurements at room temperature to be 2.29 × 103 cm2 V−1 s−1 and 2.14 × 1013 cm−2, respectively, including contribution from the InN bottom layer. The Shubnikov–de Haas results at 3 K confirm that the 2DEG has an electron density of 3.30 × 1012 cm−2 and a quantum mobility of 1.48 × 103 cm2 V−1 s−1. The experimental observations of 2DEG at the InGaN/InN heterointerface have paved the way for fabricating higher‐speed transistors based on an InN channel.
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