InAs Heterostructures Research Articles

Size, position and direction control on GaAs and InAs nanowhisker growth

The self-organized, position-controlled and parallel growth of GaAs and InAs nanowhiskers is successfully demonstrated by using a metal–organic chemical vapour deposition method. The growth takes place preferentially along the 〈 111 〉 As direction with the aid of the catalytic effect of Au nanodroplets, and not along 〈 111〉 Ga or In directions. The diameter and length of the whisker can be controlled artificially down to 10 nm and to over 1 μm, respectively. Doping and composition control of p- or n-type such as GaAs–InAs heterostructure formation are possible along the length direction of the whisker by changing the source gases. In order to control the growth position of the whisker, positioning of a Au nanodroplet is essential and realized by a lithographic method. By choosing the [111]B direction to the substrate surface and normal to the patterned side edges, and by positioning the Au nanodroplet on the side wall, the positioned planar nanowhisker growth and bridging are successfully demonstrated. The growth mechanism of the nanowhiskers is revealed by the scanning and transmission electron microscope observations. Nanometer-size Au-alloy droplets play an important role in the growth of the whiskers. The whisker growth process is governed by the vapor–liquid–solid growth mechanism.

InAsSbP/InAs LEDs for the 3.3–5.5 µm spectral range

Room-temperature LEDs, fabricated from LPE grown InAsSb(P)/InAs heterostructures, are characterised with respect to methane (3.3 /spl mu/m), carbon dioxide (4.3 /spl mu/m) and nitric oxide (5.3 /spl mu/m) optical detection. Output power as high as 50 /spl mu/W (I=1 A, 128 /spl mu/s) and FWHM as small as 0.6 /spl mu/m have been obtained for the first reported InAsSb LED emitting at 5.5 /spl mu/m.

Interband impact ionization by terahertz illumination of InAs heterostructures

Experimental studies of InAs heterostructures illuminated by far-infrared (FIR) radiation reveal an abrupt increase in the charge density for FIR intensities above a threshold value that rises with increasing frequency. We attribute this charge density rise to interband impact ionization in a regime in which ωτm∼1, where τm is the momentum relaxation time, and f=ω/2π is the FIR frequency. The dependence of the density rise on the FIR field strength supports this interpretation, and gives threshold fields of 3.7–8.9 kV/cm for the frequency range 0.3–0.66 THz.

Properties of a high‐mobility two‐dimensional electron gas in modulation‐doped quantum well structures of GaInAs/AIInAs and GaInAs/(Ga1−xAlx)InAs heterostructures

AbstractThe electronic and magnetotransport properties of the two‐dimensional electron gas (2DEG) in MBE‐grown GaInAs/AlInAs and GaInAs/Ga1−xAlxInAs heterostructures are investigated in magnetic fields up to 12 T. The quantum oscillations of the magnetoresistivity (SdH effect) and the observation of pronounced quantum Hall effect demonstrate the existence of a high‐mobility 2DEG in the GalnAs potential well. The characteristic parameters of the electronic band structure of the 2DEG are determined and are compared with self‐consistent solutions of the coupled Poisson and Schrödinger equations. The influence of hydrostatic pressure on the magnetotransport properties is studied. A surprisingly weak change of the subband occupation with pressure is revealed.

Optical analysis of InAs heterostructures grown by migration-enhanced epitaxy

The authors have investigated the interface of InAs/GaSb and InAs/AlSb grown by migration-enhanced epitaxy by photoluminescence and Raman spectroscopy. The significant effects of interface bonds, InSb or GaAs (AlAs), on the luminescence as well as phonon spectra are discussed. The confined phonon modes in both systems, InAs/GaSb and InAs/AlSb, are also compared to study the characteristic properties of InAs heterostructure.

Growth and transport properties of (Ga,Al)Sb barriers on InAs

We have investigated the transport properties of (Ga,Al)Sb–InAs heterostructures grown by molecular-beam epitaxy with the Al composition in the range of 0.3–0.5 where the alloy serves as a potential barrier for electrons in InAs. Field effect capacitors using a thick (Ga,Al)Sb barrier demonstrate the modulation of carrier densities in InAs by the application of an electric field. In the region of thin (Ga,Al)Sb, where tunneling becomes dominant, a novel negative resistance appears in InAs/(Ga,Al)Sb/InAs single-barrier structures due to the specific band alignment of this system. The results have been further elucidated under a magnetic field.

Resonant-tunnelling hot-electron transistor (RHET) using a GaInAs/(AlGa)InAs heterostructure

A common-emitter current gain of 10 has been measured at 77 K for a 100 nm-base resonant-tunnelling hot-electron transistor (RHET) using a GaInAs/(AlGa)InAs heterostructure. The current gain for 25 nm-base RHETs has reached 25, which is the highest value yet reported for hot-electron transistors, and the collector current peak-to-valley ratio has reached 15.0 for the same device.

Liquid-phase epitaxial growth of stepwise-graded InAs1−xSbx–InAs heterostructures

To alleviate the lattice mismatch for InAs1−xSbx (0<x<0.2) deposited on InAs we have employed a multilayer structure of incrementally increasing compositional steps grown by a steady state liquid-phase epitaxial growth technique. Etch pit densities and surface morphology for various substrate orientations have been studied. The resultant films possess surface cross-hatch patterns with etch pit densities of ?3×104 cm−2 for growth on (100) substrates.