Improved electron mobility in InSb epilayers and quantum wells on off-axis Ge (001) substrates

Abstract

Two types of InSb structures, epilayers and quantum wells (QWs), have been grown on on-axis and 6 -off-axis Ge (001) substrates and examined by reflection high-energy electron diffraction, transmission electron microscopy, X-ray diffraction, atomic force microscopy, and the van der Pauw and Hall effect techniques. Anti-phase domain defects, which prevail in these InSb structures when grown on on-axis Ge (001) substrates, are significantly decreased by the use of 6 off-axis Ge (001) substrates. Such off-axis substrates also lead to reductions in the densities of micro-twins and threading dislocations. Room-temperature electron mobilities in 4.0-lm-thick InSb epilayers and 25-nm-thick InSb QWs grown on 6 -off-axis Ge (001) substrates are 59 000 and 14 000 cm 2 /(V s), respectively, which are $1.5 times higher than their counterparts grown on on-axis Ge (001) substrates. These improved mobilities are the highest among the reported values for each type of structure grown on Ge (001) substrates.

High electron mobility in InSb epilayers and quantum wells grown with AlSb nucleation on Ge-on-insulator substrates

“…10, 15 We also showed that a 6 -off-axis Ge(001) substrate has a single-domain surface after oxide desorption, which reduces APD formation in the subsequent layers. The RHEED analysis in this study also showed that a similar phenomenon takes place for on-axis and 4 -off-axis GeOI substrates: APDs were created in the AlSb nucleation layer and subsequent epilayers when they were grown on an on-axis GeOI substrate.…”

“…Previously, we found that the use of a 6 -off-axis substrate is also effective in reducing MT and TD densities in InSb epilayers grown on Ge(001) substrates. 15 We evaluated the carrier density and mobility in the InSb structures using van der Pauw and Hall-effect measurements from RT to 20 K. In order to perform a systematic evaluation, we grew several sets of undoped and doped InSb epilayers and QWs with and without deposition of an initial AlSb nucleation layer. Since the Ge substrate has a low resistivity of $1 X-cm, it is difficult to interpret van der Pauw and Hall-effect measurements for an InSb epilayer directly grown on top of it.…”

“…1(b), in order to supply electrons to the QW and surface states. 6,15 The growth conditions for AlSb were evaluated by monitoring the RHEED pattern. The substrate temperature (T sub ) and the Sb 2 /Al growth-rate ratio were varied from 500 to 570 C and from 1.4 to 2.0, respectively.…”

“…More details of the experimental conditions can be found elsewhere. 10,15,20 After MBE growth, the structures were characterized by atomic force microscopy (AFM), TEM, and high-resolution x-ray diffraction (HRXRD). In addition, van der Pauw and Hall-effect measurements were performed at temperatures ranging from room-temperature (RT) to 20 K. The dominant type of carrier in the structures was determined by applying a magnetic field up to 1.3 kG.…”

“…13 It was reported that the use of off-axis substrates (e.g., Ge, Si, and SiC) reduced not only the abovementioned crystalline defects but also morphological defects of InGaAs and 4H-SiC epitaxial films, leading to the improvement of the device performance. [15][16][17] In this paper, we report an optimized growth of InSb films on an off-axis GeOI substrate, which is expected to reduce the crystalline defects and thus improve the electron mobility. We developed a method for growing high quality InSb epilayers and quantum wells (QWs) structures on GeOI-onSi(001) substrates by MBE.…”