Growth and properties of high mobility strained inverted AlInAs–GaInAs modulation doped structures

Abstract

GaInAs–AlInAs inverted modulation-doped structures exhibit degraded two-dimensional electron gas (2DEG) transport properties when grown under standard conditions. This results from the surface segregation of Si from the donor layer into the GaInAs channel layer. Consequently, the 2DEG has poor mobility due to increased ionized impurity scattering. We have obtained high mobility inverted structures through the inhibition of this surface segregation by growing the spacer layer at a greatly reduced substrate temperature. Inverted modulation doped structures optimized for high frequency device applications require the use of thin channel layers. In order to obtain a large charge density (≳ 2.3 × 1012 cm−2) with high quality transport characteristics, In-rich, strained channels are required. This paper presents the results of an investigation of the electronic and optical properties of strained, inverted, thin-channel modulation doped structures. Channel thicknesses of 50–200 Å and In compositions of 53% to 80% were investigated. A 300 K electron mobility of 13 000 cm2/V s was obtained with a sheet charge density of 2.4 × 1012 cm−2 for a 75 Å thick Ga0.27In0.73As channel.