Jul 28, 2016

Strain-driven synthesis of 〈112〉 direction InAs nanowires in V-grooved trenches on Si using InP/GaAs buffer layers

Highlights

We reported the 〈112〉 direction growth of InAs nanowires on patterned Si (001).
We proposed mechanism of 〈112〉 directions InAs nanowires and demonstrated.
We reported stacking-faults-free ZB InAs nanowires on Si (001).
InAs nanowires crystal quality was measured by TEM.

Abstract

The catalyst-free metal organic vapor phase epitaxial growth of InAs nanowires on silicon (001) substrates is investigated by using selectively grown InP/GaAs buffer layers in V-grooved trenches. A strain-driven mechanism of self-aligned 〈112〉 direction InAs nanowires growing is proposed and demonstrated by the transmission electron microscopy measurement. The morphology of InAs nanowires is tapered in diameter and exhibits a hexagonal cross-section. The defect-free InAs nanowire shows a pure zinc blende crystal structure and an epitaxial relationship with InP buffer layer.

Keywords

  • A1 Growth models
  • A3 Metal-organic chemical vapor deposition
  • B1 Nanomaterials
  • B1 Semiconducting III–V materials
        • SOURCE:Sciencedirector
          If you need more information about GaAs wafer, please visit our website: http://www.powerwaywafer.com or send us email to  powerwaymaterial@gmail.com.

Jul 26, 2016

Native oxides formation and surface wettability of epitaxial III–V materials: The case of InP and GaAs

Highlights

Wettability of binary, MOVPE grown, III–V materials (GaAs, InP, InAs) was investigated as a function of age and surface treatment.
XPS study was performed, to reveal the surface native oxides composition.
No trivial correlation between the oxide thickness/type and water drop contact angle was observed.

Abstract

The time dependent transition from hydrophobic to hydrophilic states of the metalorganic vapour phase epitaxy (MOVPE) grown InP, GaAs and InAs is systematically documented by contact angle measurements. Natural oxides forming on the surfaces of air-exposed materials, as well as the results of some typical wet chemical process to remove those oxides, were studied by X-ray photoemission spectroscopy (XPS), revealing, surprisingly, a fundamental lack of strong correlations between the surface oxide composition and the reported systematic changes in hydrophobicity.

Keywords

  • Hydrophobic surface
  • InP
  • GaAs
  • XPS
  • MOVPE
        • SOURCE:Sciencedirector
          If you need more information about GaAs wafer, please visit our website: http://www.powerwaywafer.com or send us email to  powerwaymaterial@gmail.com.

Jul 19, 2016

InGaP/GaAs heterojunction photosensor powered by an on-chip GaAs solar cell for energy harvesting

Abstract

In this study, an InGaP/GaAs heterojunction phototransistor (HPT) and a GaAs solar cell were monolithically integrated into an HPT epitaxial wafer, and the battery-free operation of the HPT was demonstrated for energy harvesting. Although the thickness and doping condition of the layers were optimized for the HPT performance, but not for the solar cell performance, the obtained short-circuit current was high enough to operate the InGaP/GaAs HPT in a two-terminal (2T) configuration. A collector photocurrent of 0.63 mA was obtained when the energy-harvesting InGaP/GaAs 2T-HPT was exposed to white light with a power density of 35 mW/cm2, and it linearly increased with the power density. For a potential application of the energy-harvesting InGaP/GaAs HPT as a photosensor in space, the device was irradiated with electrons of 1 MeV energy and 1015 cm−2 fluence. No significant degradation of the fabricated energy-harvesting 2T-HPT after the high-energy electron irradiation guarantees its battery-free operation in space.

 Introduction

A heterojunction phototransistor (HPT) is more attractive as a photosensor than a photodiode because of its high photoresponse even at low bias voltage and immunity from avalanche noise.13) In particular, the GaAs-based HPT with an AlGaAs emitter demonstrated a high performance. Recently, the InGaP emitter has replaced the AlGaAs emitter in the AlGaAs/GaAs HPT owing to its superior material properties.4) The photosensor may be widely used in space, where it needs to be operated without a battery. An HPT has a process compatibility with a heterojunction bipolar transistor (HBT) for the fabrication of monolithically integrated photoreceivers.5) The InGaP/GaAs HPT also has good compatibility with the GaAs heteroface solar cell for a battery-free operation. Solar cells made of III–V compound semiconductors have been developed and used in space owing to their high conversion efficiency, lower temperature coefficient, and superior radiation resistance.69) The significant potential of high-efficiency GaAs heteroface solar cells for space applications has been extensively investigated by many researchers.1017) Compared with Si, which has been widely used as a material of terrestrial solar cells, III–V compound semiconductors have a superior radiation resistance for the same electron energy and fluence. In particular, the InGaP solar cells demonstrated a radiation resistance superior to that of GaAs solar cells. Since the migration energy of radiation-induced defects and the activation energy of defect annealing in InGaP are lower than those in GaAs, InGaP has a higher radiation resistance than GaAs.18) In this study, radiation resistant InGaP was used as a window layer in a GaAs heteroface solar cell.
In space, high-energy electron or particle irradiation often induces a significant degradation of the performance of semiconductor devices. Since the battery-free operation of an InGaP/GaAs HPT monolithically integrated with a GaAs solar cell is also proposed for use in space in this paper, the effects of high-energy electron irradiation on the fabricated energy-harvesting HPTs were studied by 1 MeV electron irradiation.

Keywords

  • GaAs/Si ; 
  •  AlGaAs/GaAs HPT 
    • SOURCE:iopscience
      If you need more information about GaAs wafer, please visit our website: http://www.powerwaywafer.com or send us email to  powerwaymaterial@gmail.com.