Persistent photoconductivity and properties of the Two‐Dimensional electron Gas in modulation‐doped GaInAs/AlInAs heterostructures after illumination

Abstract

The properties of the two-dimensional electron gas (2DEG) in MBEgrown low carrier density Gao.47Ino.saAs/Alo.48Ino.52As heterostructures after illumination at low temperatures have been investigated. A strong persistent photoconductivity and drastic changes of low temperature electronic properties were observed. The pronounced changes of the quantum oscillations of the magnetoresistivity (Shubnikov-de Haas effect) and of the quantum Hall effect clearly reveal an important increase of both electron concentration and carrier mobility in the two-dimensional interface layer. The variations of the electronic properties are attributed to photoexcitation of electron-hole pairs in the GaInAs layer.Die Eigenschaften des zweidimensionalen Elektronengases (2DEG) wurden in MBEgewachsenen G~.~~I n~.~A s / A l~,~I~.~~A~H e t e r~t r u k t u r e n mit geringen Ladungstragerkonzentrationen nach Beleuchtung bei tiefen Temperaturen untersucht. Eine starke eingefrorene Photoleitfiihigkeit (PPC, persistent photoconductivity) und drastische Veranderungen der elektronischen Eigenschaften bei tiefen Temperaturen wurden beobachtet. Die deutlichen Veriinderungen in den Quantenoszillationen des Magnetowiderstandes (Shubnikov-de Haas-Effekt) und im Quanten-Hall-Effekt belegen eindeutig sowohl eine Erhiihung der Elektroncndichte, als auch der Ladungstragerbeweglichkeit in der zweidimensionalen Schicht am Heteroubergang. Die Variationen der elektronischen Eigenschaften werden mit einer lichtinduzierten Anregung von Elektron-Loch-Paaren in der GaInAs-Schicht erklart.

Persistent photoconductivity in a two-dimensional electron gas system formed by an AlGaN/GaN heterostructure

“…Similar behaviors have been observed previously for the 2DEG system in AlGaAs/GaAs 17 and AlInAs/GaInAs heterostructures at low temperatures. 18 Recently, an improved electrical performance of AlGaN/GaN modulation-doped field-effect transistors due to optical excitation has been observed, 4 which may be related to the photoinduced increase in carrier density and mobility in the 2DEG channel seen here.…”

Ultra-sensitive photoresponse and persistent photoconductivity in modulation doped Ge/SiGe and Si/SiGe heterostructures

“…A similar PPC effect and change in 2D density has also been observed in Si and SiGe channel structures (see figures 1(a) and (b)). Earlier reports on PPC in GaAlAs/AlInAs [2] and Si/SiGe [9] heterostructures have confirmed, using low-temperature Shubnikov-de Haas experiments, that illumination causes an increase in the channel density. When the illumination is turned off the decay of the enhanced conductivity in our samples was found to be a non-exponential function of time, which can be fitted to a logarithmic function as shown in figure 4.…”

“…Persistent photoconductivity (PPC) in bulk semiconductors [1] and modulation doped semiconductor heterostructures is a well known effect [2][3][4][5][6]. The term PPC describes the observation that the conductivity of various semiconductors is greatly enhanced after illumination at low temperatures and that this high-conductivity state is maintained for many hours after turning off the illumination.…”

“…Al x Ga 1−x As is known to exhibit PPC and this property was exploited to demonstrate the possibility of writing persistent metallic patterns [8] which could be used as optical gratings for switching, holography and high-density data storage applications. Saffian et al [2] have discussed in detail PPC and drastic changes in low-temperature electronic properties of the two-dimensional electron gas (2DEG) in modulation doped GaInAs/AlInAs heterostructures after illumination. In all the above-mentioned reports the absolute intensity of illumination onto the sample is not known.…”