Abdelkader Abderrahmane

High photosensitivity few-layered MoSe2 back-gated field-effect phototransistors

In this paper, we report on the fabrication and optoelectronic properties of high sensitive phototransistors based on few-layered MoSe2 back-gated field-effect transistors, with a mobility of 19.7 cm² V⁻¹ s⁻¹ at room temperature. We obtained an ultrahigh photoresponsivity of 97.1 AW⁻¹ and an external quantum efficiency (EQE) of 22 666% using 532 nm laser excitation at room temperature. The photoresponsivity was improved near the threshold gate voltage; however, the selection of the silicon dioxide as a gate oxide represents a limiting factor in the ultimate performance. Thanks to their high photoresponsivity and external quantum efficiency, the few-layered MoSe2-based devices are promising for photoelectronic applications.

High Temperature Hall sensors using AlGaN/GaN HEMT Structures

Hall effect sensors are the most widely used magnetic sensors, and are commonly fabricated using narrow band-gap semiconductors such as InSb and GaAs. However, the operation of InSb and GaAs-based Hall sensors is unstable at elevated temperatures. Here, we exploited the fact that gallium nitride- (GaN) based wide band-gap (3.4eV) semiconductors have high breakdown electric field strength and are robust at elevated temperatures and tested the high temperature electrical characteristics of AlGaN/GaN heterostructure micro-Hall effect sensors with a two-dimensional electron gas (2DEG). The AlGaN/GaN heterostructures had an electron mobility of 1360 cm2/Vs and a 2DEG density of 1.0 × 1013 cm−2. The supply-current-related sensitivity (SCRS) was 77VA−1T−1 at room temperature. Notably, the temperature coefficient of the Hall voltage was +0.05 %/°C near room temperature, and SCRS was 67 VA−1T−1 at 400°C. The results for AlGaN/GaN were compared with those for AlGaAs/GaAs and AlInSb/InAsSb/AlInSb QW Hall effect sensors.

Robust Hall Effect Magnetic Field Sensors for Operation at High Temperatures and in Harsh Radiation Environments

We describe the fabrication and magnetoelectric properties of robust, high sensitivity Hall effect sensors fabricated using AlGaN/GaN and AlInSb/InAsSb/AlInSb heterostructures with a two-dimensional electron gas at the heterointerface. The sensitivity of AlInSb/InAsSb/AlInSb heterostructure clearly degrades above ~ 150°C. The AlGaN/GaN 2DEG Hall sensors were stable up to at least 400 °C and even after irradiation of 380 keV protons with a fluence of 1×1014 cm- 2, where AlInSb/InAsSb/AlInSb heterostructure showed an increase in the sheet carrier density. The feasibility of applications of the AlGaN/GaN and AlInSb/InAsSb/AlInSb Hall sensor for harsh radiation environment is discussed.

Effect of proton irradiation on AlGaN/GaN micro-Hall sensors

The magnetoelectric properties of AlGaN/GaN micro-Hall effect sensors were studied after 380 keV proton irradiation. After irradiation the current-voltage measurements, stability of the magnetic sensitivity of the sensors, and the sheet electron density were degraded with a dramatic decrease of the electron mobility at high temperatures. Raman spectroscopy showed a degradation in the crystalline quality of GaN crystal, but there was no change in the strain.

Effects of Proton Irradiation on the Magnetoelectric Properties of 2DEG AlGaN/GaN Micro-Hall Sensors

The effects of irradiating AlGaN/GaN micro-Hall sensors with 380 keV protons on were investigated by magnetoresistance measurements. The sheet resistance increased after irradiation with a proton dose of 1×1013 cm−2 due to the decrease of carrier mobility rather than the decrease of sheet carrier density. Our experiments showed that AlGaN/GaN two-dimensional electron gas (2DEG) structures are good strong candidates for Hall sensors operable in harsh radiation environments.

Proton Irradiation Enhancement of Low-Field Negative Magnetoresistance Sensitivity of AlGaN/GaN-Based Magnetic Sensor at Cryogenic Temperature

The longitudinal and transverse magnetoresistances of AlGaN/GaN heterostructure-based micro-Hall sensors were compared with samples irradiated with protons with an energy of 380 keV and fluence of 1014 (protons/cm2). Increases in the elastic and inelastic scattering were deduced from weak localization behavior in both samples. The AlGaN/GaN micro-Hall sensors showed stable magnetic sensitivity in non and irradiated samples and increased resistivity after proton irradiation yielded an enhanced magnetoresistance sensitivity in nonirradiated sensors from 160 to 417 VA-1T-1. The minimum detectable magnetic field of irradiated micro-Hall sensors determined from magneto-voltage measurements at ~4 K was similar to the minimum detectable magnetic field in the nonirradiated sensors.

Effect of Proton Irradiation on 2DEG in AlGaN/GaN Heterostructures

Low temperature Hall effect measurements were carried on AlGaN/GaN micro-Hall effect sensors before and after irradiation with 380 keV and fluence of 1014 protons/cm2 protons. The sheet electron density after irradiation did not show significant changes but there was a dramatic decrease in the electron mobility of the heterostructures. Prior to irradiation, the observation of well-defined Landau plateaus in the Hall resistance and Shubnikov-de Haas oscillations (SdH) at 4.5 T was indicative of the high quality the heterojunction confining the two-dimensional electron gas (2DEG) at the AlGaN/GaN interface of micro-Hall effect sensors. In contrast, the Landau plateaus disappeared after irradiation and the threshold magnetic field required for the observation of the SdH increased, which was accompanied by a decrease of the electron mobility. Temperature dependent magnetoresistance measurements were used to deduce the effective mass and the quantum scattering time before irradiation. A negative magnetoresistance was observed at low magnetic fields which is related to weak localization and parabolic negative magnetoresistance attributed to electron-electron interaction in both samples.

Partial recovery of the magnetoelectrical properties of AlGaN/GaN-based micro-Hall sensors irradiated with protons

The effect of annealing on the magnetoelectrical properties of proton-irradiated micro-Hall sensors at an energy of 380 keV and very high proton fluences was studied. Recovery of the electron mobility and a decrease in the sheet resistance of the annealed micro-Hall sensors, as well as an enhancement in their magnetic sensitivity were reported. Trap removal and an improvement in the crystal quality by removing defects were confirmed through current–voltage measurements and Raman spectroscopy, respectively.

Effect of annealing on proton irradiated AlGaN/GaN based micro-Hall sensors

The effect of annealing at 673 K on irradiated micro-Hall sensors irradiated with protons at 380keV and fluences of 1014, 1015 and 1016 protons/cm2 is reported. Cathodoluminescence measurements were carried out at room temperature before and after annealing and showed improvement in the band edge band emission of the GaN layer. After annealing a sensor irradiated by 1015 protons/cm2 the device became operational with improvements in its magnetic sensitivity. All irradiated sensors showed improvement in their electrical characteristics after annealing.

High Proton Radiation Tolerance of InAsSb Quantum-Well-Based micro-Hall Sensors

Tolerance of AlInSb/InAsSb/AlInSb heterostructures quantum-well-based micro-Hall sensors against proton irradiation of 380 keV and proton fluence in the range 1011 and 1016 (proton/cm2) is reported. Defects and deep levels induced by proton irradiation into the heterostructures caused decreases in the mobility of the micro-Hall sensors. Degradation of the magnetic sensitivity started at a proton fluence of 1013 (proton/cm2) and continued with increasing proton fluence. The variation of the micro-Hall sensors sensitivity was minimal in lowdoped AlInSb/InAsSb/AlInSb heterostructure quantum wells. These micro-Hall sensors were operable even at proton fluence of 1016 (proton/cm2), which makes these devices suitable for space applications with lifetime of thousands of years in the outer space.