Low‐Temperature Electron Transport in Quasi‐Two‐Dimensional Systems

Abstract

A theoretical approach including multi-subband coupling is applied to electron transport in quasitwo-dimensional systems. This results in a modified contribution of the several scattering mechanisms to the total scattering rate. Taking into account the dominant scattering mechanisms the low-temperature mobility is calculated in the electric quantum limit and is compared with experimental data for heterojnnckions and single quantum wells (particularly consisting of Gal -*. AI,As/GaAs).Ein theoretisches Konzept mit verbesserter Einbeziehung der Rlultisubbandkopplung wird auf den Elektronentransport in quasizweidimensionalen Systemen angewandt. Dies fiihrt zu einem verhinderten Beitrag der einzelnen Streumechanismen zur Gesamtstreurate. Die Tiefternperaturbeweglichkeit wird fur einfache Potentialtopfe und Heteroiibergilnge (speziell aus Gal -%.-AI,As/GaAs) im ,,electric quantum limit " unter Einbeziehung der dominanten Streumechanismen berechnet und mit experimentellen Dnten verglichen.

Conductance of quantum wires with self-consistent level broadening

“…No divergence arises from the term proportional to the real part of the Green function and this term can be neglected. The quantity fG1 is the position-dependent relaxation time in the Boltzmann theory as analysed by Ziep et a1 (1986) and by Pratsch andSuhrke 1988,1989) for the Q2D case. It can be easily verified that with the subband relaxation time Za(Eek,) = d 2 r L qi(rl)f<l(Eak,;rl)* (38) It should be noted that equation (38) differs from the usual results of the Boltzmann theory for low-dimensional systems based on Fermi's golden rule for the transition probability (Ando et a1 1982).…”

“…In this case the inverse subband relaxation time r , l ( E n k , ) = / d 2 r l q i ( r l ) f B ( E e k y k , ; rl) (39) A arises from integration over the cross section already in the transport equation. This may lead to remarkable differences in the dependence of conductance on temperature and carrier concentration (Ziep et a1 1986, Pratsch and Suhrke 1988,1989.…”

Electron Transport in Quasi‐Two‐Dimensional Systems. Influence of Intersubband Scattering

“…2) there is no drop of the mobility at N p t because of the very strong energy dependence of the relaxation time in the electric quantum limit (cf. [2]). Other theoretical papers obtain a drop of the mobility for this scattering mechanism, but Ap vanishes in the limit d -t 00, In the temperature dependence of the mobility significant differences to the behaviour in the electric quantum limit are observed if the concentration is near N F t .…”

“…I n [ 2 ] it has been pointed out that in case of the electric quantum limit there are some new results for the dependence of the mobility on electron concentration and temperature using (2). I n this paper the occupation of the first excited subband is included into the calculatiod taking into account the dominant scattering mechanisms a t low temperatures (up to 50 K), i.e.…”