Superlattice Intermediate Layers Research Articles

Quality Improvement of GaN on Si Substrate for Ultraviolet Photodetector Application

GaN is grown on an Si substrate using metal-organic vapor-phase epitaxy. Compared with the full width at half maximum values from X-ray diffraction patterns and photoluminescence spectra of conventional GaN on the Si substrate, those of GaN on the Si substrate with the insertion of various-temperature AlN nucleation layers and Al0.3Ga0.7N/GaN superlattice intermediate layers are reduced by 34.9% and 25.6%, respectively. In addition, Raman spectra show that residual stress on the GaN epilayers decreased by 0.35 GPa. The c-lattice parameter of the GaN epilayer is 5.1844 Å, which is close to that of an unstrained GaN layer. Ultraviolet metal-semiconductor-metal photodetectors are fabricated on an almost-crack-free GaN surface. The dark current of a photodetector on the Si substrate is 2.4 ×10-11 A at a 9 V applied bias, which is one order of magnitude smaller than that of a photodetector on a conventional sapphire substrate. The maximum quantum efficiency value of a photodetector on the Si substrate is ~ 97% with an incident light wavelength of 360 nm and a 9 V applied bias.

Investigation of GaN crystal quality on silicon substrates using GaN/AlN superlattice structures

AbstractThe crystal quality of GaN thin film on silicon using GaN/AlN superlattice structures was investigated. The growth was carried out on Si(111) for GaN(0001) in a metal‐organic vapor phase epitaxy system. Various GaN/AlN superlattice intermediate layers have been designed to decrease the dislocation density. The results showed that the etch pit density could be greatly reduced by one order of magnitude. Cross‐sectional transmission electron microscopy (XTEM) study confirmed the efficiency of GaN/AlN superlattice in blocking threading dislocation propagation in GaN crystal. The design of nine period GaN/AlN (20nm/2nm) superlattice has been evidenced to be effective in reducing the dislocation density and improving the crystal quality. In addition, the dislocation bending in GaN/AlN interface and dislocation merging is investigated. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Very low dislocation density GaAs on Si using superlattices grown by MOCVD

GaAs was grown on Si substrates by metalorganic chemical vapor deposition using GaAs/GaAsP strained layer superlattice (SLS) intermediate layers. The dislocation density decreases at the interface between the GaAs and the SLS, hence for maximum effect GaAs was grown on Si using three SLSs separated by GaAs layers. A low etch pit density GaAs-on-Si of the order of 10 5 cm -2 was obtained by using an intermediate layer of GaAs/GaAsP SLSs, an AlAs/GaAs superlattice and thermal-cycle annealing.

Low etch pit density GaAs on Si grown by metalorganic chemical vapor deposition

GaAs was grown on a Si substrate by metalorganic chemical vapor deposition using GaAs/GaAsP strained-layer superlattice (SLS) intermediate layers. The dislocation density decreases at the interface between GaAs and the SLS, but does not decrease in the SLS. When a GaAs/GaAsP SLS is used as the intermediate layer, part of the threading dislocation propagates into the top GaAs layer because of the lattice mismatch of GaAs and SLS. The low etch pit density of (3–5)×105 cm−2 was obtained by using the intermediate layer of a GaAs/GaAsP SLS and an AlAs/GaAs superlattice with thermal cycle annealing.

Tem Characterization of Dislocations in GaAs-ON-Si Heterostructures Wite Sjpereatlice Intermediate Iayers

ABSTRACTGaAs was grown on Si substrate by metalorganic chemical vapor deposition using GaAs/GaAsP strained layer superlattice (SLS) intermediate layers. The dislocation density decreases at the interface between GaAs and SLS, but does not decrease in the SLS. When GaAs/GaAsP SLS is used as the intermediate layer, a part of the dislocation propagates into the top GaAs layer because of the lattice mismatch of GaAs and SLS. The low etch-pit-density of (3-5) x 105 cm−2 was obtained by using the intermediate layer of GaAs/GaAsP SLS and AlAs/GaAs superlattice with thermal-cycle annealing.

AlGaAs/GaAs transverse junction stripe lasers fabricated on Si substrates using superlattice intermediate layers by MOCVD

TJS lasers are fabricated on Si substrates by diffusing Zn using sputtered SiO 2 as a mask, and the lasing properties are measured. The minimum threshold current of 379 mA and a differential efficiency of 2.2 percent have been obtained. The detailed fabrication procedure and laser characteristics are described in this paper.

Selective MOCVD Growth of GaAs on Si Substrate with Superlattice Intermediate Layers

GaAs was grown on a Si substrate through a SiO2 mask using superlattice intermediate layers by MOCVD. Single and poly crystalline GaAs layers were grown on the Si substrate and on the mask, respectively. Ridge growth was observed at the substrate/mask interface. The relationship between the ridge growth properties (the shape and the height) and the growth conditions were made clear. The ridge growth rate increases exponentially with approaching the interface. The ridge shape was determined by the surface migration and the gradient in the gas phase concentration of the Ga active species. The ridge growth height of GaAs grown on GaAs was higher than that grown on Si. These results could be explained by taking account of the difference in the surface migration length of the Ga active species on GaAs and Si substrates.

MOCVD Growth of III-V Compound Semiconductors on Si Substrates Using Strained Superlattice Intermediate Layers

MOCVD Growth of III-V Compound Semiconductors on Si Substrates Using Strained Superlattice Intermediate Layers

Heteroepitaxy of GaAs on Si by MOCVD

ABSTRACTThe stress and strain of GaAs on Si grown by using strained superlattice intermediate layers and a two-step growth method are characterized by the photoluminescence, X-ray diffraction and the curvature radius. The strain of GaAs grown using strained superlattice intermediate layers is smaller than that grown by the two-step growth method.

GaAlAs/GaAs TJS Lasers on Si Substrates Operating at Room Temperature Fabricated by MOCVD

GaAlAs/GaAs TJS (transverse junction stripe) laser diodes were fabricated on p-Si substrates using strained super lattice intermediate layers. The diodes have lased at room temperature (27°C) pulsed conditions. The lowest threshold current is 379 mA.

Band Gap Energy and Stress of GaAs Grown on Si by MOCVD

The band gap gap energy and stress of GaAs grown on Si using (GaP/GaAsP) and (GaAsP/GaAs) superlattice intermediate layers were measured by electro-reflectance and wafer bending. It was found that high-density dislocations or defects which can relax stress exist during the early stages of the growth and decrease with the growth sequence; the growth temperatures have significant effects on crystal perfection.

Deep Levels in GaAs Grown Using Superlattice Intermediate Layers on Si Substrates by MOCVD

Deep levels in MOCVD-grown GaAs using superlattice intermediate layers on Si substrates were investigated by DLTS. Electron traps at 0.44 and 0.73 eV were observed in the undoped n-type GaAs grown on (100)2° off Si substrates while only a 0.73-eV trap was detected in GaAs on a GaAs substrate. The deep-level concentration in GaAs/Si and the capture cross section of a 0.44-eV trap decreased and the half width of the 0.44-eV trap increased with increasing GaAs thickness. The 0.73-eV trap concentration increased upon decreasing the curvature radius of the wafer by polishing the back side of the Si substrate; however, that of 0.44 eV was unchanged. These observations suggest that the 0.44-eV trap is due to Si-defect complexes changing their shapes with the GaAs thickness and that of 0.73 eV is caused by point defects.

Room-temperature laser operation of AlGaAs/GaAs double heterostructures fabricated on Si substrates by metalorganic chemical vapor deposition

AlGaAs/GaAs double heterostructure laser diodes have been fabricated on Si substrates using GaP/(GaP/GaAsP) superlattice/(GaAsP/GaAs) superlattice intermediate layers grown by metalorganic chemical vapor deposition. A threshold current density at 16.5 °C and a characteristic temperature T0 of 4.9 kA/cm2 and 179 K respectively have been obtained for the diode on Si substrate.