The influence of Cr concentration on time resolution of GaAs detectors

Investigated in this work were the influence of Cr dopant concentration and technological conditions of doping on photoconductivity (PhC) kinetics, dependence of PhC signal magnitude on voltage applied as well as the dynamic range of a photodetector based on semi-insulating GaAs:Cr. PhC relaxation was measured using a broadband system of registration in the picosecond pulse range, which is based on the oscillograph C7-19, CCD camera and personal computer. Mechanisms of recombination that influence on fast and slow components of the PhC signal were studied. The shortest time of PhC relaxation τ ~ 2.10⁻¹⁰ s was observed in GaAs:Cr samples for the chromium dopant concentration NCr ~ 3.10¹⁷ cm−3. We have found a linear increase of the fast component of PhC with the intensity of excitation as well as a weak dependence at small levels and saturation at the high ones of excitation for the PhC slow component

Photoresponse of Schottky-barrier detector under strong IR laser excitation

Peculiarities of the photovoltaic effect in Ti/n-Si Schottky contact have been studied experimentally under infrared (IR) laser excitation at wavelengths 2.79, 3, 5, 7 and 10.6 mm. We demonstrate that strong laser excitation gives rise to the photovoltage even if an incident photon energy is lower than Schottky barrier height. In this case the photovoltage as a function of light intensity follows a power-law dependence with the power greater than unity (2...6). The results are interpreted from the viewpoint of electron emission over the potential barrier due to multiphoton or multistep light absorption at the metal-semiconductor interface

New GaAs infrared detector

We report our results of experimental study of photovoltage induced by pulsed CO2 laser in GaAs p-n and 1-h junctions. We demonstrate that photoemission of hot carriers across the potential barrier and the crystal lattice heating are the dominant mechanisms in the photovoltage formation. The obtained results show that hot-carrier effects in inhomogeneous GaAs can be used to detect very short infrared laser pulses

Microwave sensor based on modulation-doped GaAs/AlGaAs structure

We propose a microwave diode based on a modulation-doped GaAs/Al(0.25)Ga(0.75)As structure. The principle of the diode operation relies on a non-uniform heating of the two-dimensional electron gas in microwave electric fields arising due to the asymmetric shape of the device. The voltage sensitivity of the diode at room temperature is dose to 0.3 V W(exp -1) at 10 GHz, which is comparable to the value obtained using similarly shaped and sized diodes based on bulk n-GaAs. At liquid nitrogen temperature, the voltage sensitivity strongly increases reaching a value of 20 V W(exp -1) due to the high mobility of the two-dimensional electron gas. The detected signal depends linearly on power over 20 dB, until hot-electron real-space-transfer effects begin to predominate. We discuss noise temperature measurements at 10 GHz, consider the frequency dependence of the voltage sensitivity in the microwave range and compare the performance data of the proposed device and the asymmetrically shaped bulk GaAs diode within the 10 GHz-2.5 THz frequency range

THz/subTHz detection by asymmetrically-shaped bow-tie diodes containing 2DEG Layer

We present asymmetrically-shaped bow-tie diodes based on a modulation-doped GaAs/AlGaAs structure. One of the bow-tie leaves is metallized in order to concentrate the incident radiation into the apex of the other half which contains the 2DEG layer: Here the electrons are heated non-uniformly by incident radiation inducing a voltage signal over the ends of the device. The diode sensitivity at room temperature within 10 GHz - 0.8 THz is close to 0.3 V/W, while with an increase of frequency up to 2.52 THz it decreases due to weaker coupling. We consider options to improve the operation of the device

Asymmetrically - shaped diodes for microwave - submillimeter sensing

We present a concept and possible applications of asymmetrically-shaped diodes fabricated from different types of semiconductors, i.e. non-uniform GaAs, n-Si and modulation-doped GaAs/Al(0.25)Ga(0.75)As structures. The devices can be used to detect electromagnetic radiation within a very-broad frequency band ranging from 10 GHz up to 2.5 THz (non-uniform GaAs diode) and for very intense pulsed radiation up to 10 kW (in the case of n-Si-based device)