Interband scattering in mobility in GaAs-GaAlAs heterostructures

2015

This paper reviews hot carrier effects in 2D polar semiconductors (quantum wells), with special emphasis on the GaAs system due to its higher electron mobility and direct wider band-gap. After briefly introducing the basic concepts of electron transport mechanism, we discuss theoretical calculations of current density-channel voltage characteristic for hot electrons in this quantum well structures at different lattice temperatures, namely 27K,50K, 77K and 120K on a displaced Maxwellian model, incorporating deformation potential acoustic and polar optic phonon scattering. The results are obtained from our calculations for quantum well size 100 Å. The electron mobility variations with these temperatures are also shown.

Semiconductor Physics Quantum Electronics and Optoelectronics, 2013

The temperature dependence of the electron lateral mobility in quantum wells of the GaAs/InGaAs/GaAs heterostructures with delta-like doping has been studied. Two types of sample doping -in the quantum well and in the adjacent barrier at a small distance from the well -were used. In the case of shallow wells, in such structures the experimental results may be well described by known electron scattering mechanisms taking into account the shape of real envelope wave functions and band bending due to non-uniform distribution of the positive and negative space charges along the growth direction of heterostructure layers. In the case of delta-like doping in the well, a good agreement between experiment and calculations is achieved, if one takes into account a contribution to electron transport of the states of the impurity band formed by the deltaimpurity beneath the bottom of the lowest quantum subband.

Journal of Applied Physics, 2003

We calculate the intersubband absorption linewidth 2Γop in quantum wells (QWs) due to scattering by interface roughness, LO phonons, LA phonons, alloy disorder, and ionized impurities, and compare it with the transport energy broadening 2Γtr = 2h/τtr, which corresponds to the transport relaxation time τtr related to the electron mobility µ. Numerical calculations for GaAs QWs clarify the different contributions of each individual scattering mechanism to the absorption linewidth 2Γop and transport broadening 2Γtr. Interface roughness scattering contributes about an order of magnitude more to the linewidth 2Γop than to the transport broadening 2Γtr, because the contribution from the intrasubband scattering in the first excited subband is much larger than that in the ground subband. On the other hand, LO phonon scattering (at room temperature) and ionized impurity scattering contribute much less to the linewidth 2Γop than to the transport broadening 2Γtr. LA phonon scattering makes comparable contributions to the linewidth 2Γop and transport broadening 2Γtr, and so does alloy disorder scattering. The combination of these contributions with significantly different characteristics makes the absolute values of the linewidth 2Γop and transport broadening 2Γtr very different, and leads to the apparent lack of correlation between them when a parameter, such as temperature or alloy composition, is changed. Our numerical calculations can quantitatively explain the previously reported experimental results.

Physica Status Solidi (a), 1994

The present work is seeking to trace a quantum well character in the functionality of the active epitaxial layer of semiconductor homostructures as underlying the occurrence of a negative differential mobility in the persistent photoconductive response of illuminated devices. The proposed scheme is argued to adequately interpret the characteristics of a wide variety of differently prepared n-type GaAs epitaxial layer samples.

Semiconductor Science and Technology, 2014

Temperature and nitrogen dependence of 2D carrier mobility in as-grown and annealed Ga 1−x In x N y As 1−y /GaAs quantum well (QW) structures (x = 0.32; y = 0, 0.009, and 0.012) are investigated. An analytical model that accounts for the most prominent scattering mechanisms is used to explain the characteristic of temperature dependence of the carrier mobility. An expression for alloy scattering-limited mobility in N-related alloys is developed to explain the behavior of hole mobility for N-containing p-type samples. Analytical modeling of temperature dependence of the electron mobility indicates that N-related alloy scattering and interface roughness scattering are the dominant mechanism at the entire temperature range of interest. The temperature insensitivity of the electron mobility is explained in terms of the overriding effect of N-related alloy scattering and high 2D electron density. A deviation between theoretical and experimental electron mobility at low temperatures is observed not to have any dependency on N concentration. We, therefore, suggest that C NM interaction parameter of the band anti-crossing (BAC) model must be defined as temperature dependent in order to explain the observed low temperature characteristics of electron mobility. The hole mobility is mainly restricted by interface roughness and alloy scatterings at temperatures lower than 100 K, whilst high temperature hole mobility is drastically affected from optical phonon scattering. Moreover, the hole mobility at high temperatures exhibits an N-independent characteristic and hole density starts to increase at temperatures above 70 K, which is explained using the concept of parallel conduction. Extraction of the hole density in each transport channel (QW and barrier) by using a simple parallel conduction extraction method (SPCEM) shows that, in p-type samples, low temperature hole mobility takes place in quantum well, while as temperature increases barrier channel also contribute to the hole mobility and becomes dominant at high temperatures. The experimental and calculated Hall mobility results reveal that thermal annealing has decreased interface roughness and alloy scatterings.

Central European Journal of Physics, 2008

The mobility of electrons in vertical transport in GaAs/Ga1−y Aly As barrier structures was investigated using geometric magnetoresistance measurements in the dark. The samples studied had Ga1−y Aly As (0 ≤ y ≤ 0:26) linearly graded barriers between the n+-GaAs contacts and the Ga0:74Al0:26As central barrier, which contain N w (=0, 2, 4, 7 and 10) n-doped GaAs quantum wells. The mobility was determined as functions of (i) temperature (80–290 K) at low applied voltage (0.01–0.1 V) and (ii) applied voltage (0.005–1.6 V) at selected temperatures in the range 3.5–290 K. The experimental results for the temperature dependence of low-field mobility suggest that space-charge scattering is dominant in the samples with N w =0 and 2, whereas ionized impurity scattering is dominant in the samples with N w =4, 7 and 10. The effect of polar optical phonon scattering on the mobility becomes significant in all barrier structures at temperatures above about 200 K. The difference between the measured mobility and the calculated total mobility in the samples with N w =4, 7 and 10, observed above 200 K, is attributed to the reflection of electrons from well-barrier interfaces in the quantum wells and interface roughness scattering. The rapid decrease of mobility with applied voltage at high voltages is explained by intervalley scattering of hot electrons.

Le Journal de Physique Colloques, 1987

O s c i l l a t o r y s t r u c t u r e i s observed i n forward biased dI/dV and d21/dV2 curves of conventional GaAs/GaAlAs h i g h e l e c t r o n m o b i l i t y t r a n s i s t o r samples a t l i q u i d helium temperature using modulation techniques. These o s c i ll a t i o n s can be explained by Fowler-Nordheim tunneling. From t h e p o s i t i o n of t h e o s c i l l a t i o n s t h e conduction band d i s c o n t i n u i t y i s determined a s a f u n c t i o n of t h e aluminum concentration X. For samples having an aluninun concentration between 0.

Physical Review B

A theoretical model was formulated for electron scattering in a two-dimensional electron gas confined in a triangular potential well. For the first time, the effects of intersubband scattering were included. An inherent mobility limit is imposed by phonon, alloy, and remote impurity scattering. Intersubband scattering was found to play a significant role in determining this mobility limit. The model accounted very satisfactorily for the reported electron mobility characteristics in GaAs-GaA1As heterostructures. The two-dimensional electron gas confined at a GaA1As-GaAs interface has received a great deal of attention' 6 because its unique transport characteristics play a key role in a new generation of ultra-high-speed semiconductor devices. Thus, in "selectively doped" GaAlAs-GaAs heterostructures, electrons confined at the GaAs side of the interface and separated from their parent donors, which are in GaAlAs, have exhibited mobilities as high as 2& 10 cm'/Vs;~this value is about one order of magnitude greater

physica status solidi (b), 1993

A theoretical model for the calculation of the mobility of a two-dimensional hole gas (2DHG) supported by a heterojunction is presented. Different scattering mechanisms that put a limit to the inherent mobility of the 2DHG system, like the background impurity scattering, remote impurity scattering, deformation potential, and piezoelectric acoustic phonon scattering, and polar optical phonon scattering, have been included. Dynamic screening of the hole gas has been derived. Screening plays a very important role in the scattering of the heavier hole gas than for the lightcr electrons. A discrepancy bctween the experimental and the theoretical effective hole masses existing in earlier theoretical models has been overcome in the present communication. ') 92, Acharya Prafulla Chandra Road, Calcutta 700009, India.

Journal of Luminescence, 2000

We show that interaction-assisted modes of transport play a role in the energy relaxation of excitons in disordered GaAs quantum wells. Semitransparent gold "lms are found to induce a blue shift in the photoluminescence spectrum of disordered wells. We interpret the result in terms of a long-range electromagnetic hopping coupling suppressed by image dipoles in the gold. The results are supported by Monte Carlo simulations of electromagnetically-assisted exciton hopping using hop rates modi"ed by the gold layer.