Growth of single-domain GaAs (100) layers on double-domain Si (100) substrates by molecular beam epitaxy has been investigated. It has been shown that domain orientation of the top layer of GaAs depends on the surface structure of a buffer layer. The size of atomic step heights on the Si surface and the As-Si interaction temperature before film growth are not important factors in controlling domain orientation. Suppression of an antiphase disorder is explained in terms of nonstoichiometric antiphase boundary annihilation operative during growth.
A method to reduce the density of oval defects originating from pregrowth surface particulates and other contaminants for GaAs layers grown by molecular beam epitaxy (MBE) is presented. It appears that if a thin GaAs buffer layer is deposited by alternately supplying Ga atoms and As4 molecules to a GaAs substrate, prior to further growth by MBE, the density of the oval defects in the final layer is reduced reproducibly by a factor of 7, from about 490 to 70 cm−2, when compared with that obtained using MBE alone under closely similar conditions. The improved surface morphology produced by the pulsed beam method is thought to be related to initial film growth which proceeds likely in a two-dimensional layer-by-layer fashion.
GaAs layers were grown on Si (001) substrates by molecular beam epitaxy (MBE) and migration enhanced epitaxy (MEE). They were examined by transmission electron microscopy, doublecrystal X-ray diffraction and Rutherford backscattering/channeling technique. Initial layer growth in both MEE and MBE was governed by three-dimensional nucleation but a stronger tendency for GaAs islands to align along the surface steps of Si was observed in the case of MEE. There was no measurable tilt between the (001) planes of GaAs and Si if growth was initiated by MEE at low temperature, prior to further growth by MBE at higher temperatures. On the contrary, the tilt angle was 0.34• when the entire structure was prepared by conventional two-step MBE. Rutherford backscattering measurements indicated a significant reduction in the density of defects throughout MEE/MBE GaAs in comparison with MBE GaAs.
Interdigital, planar photodetectors were fabricated from annealed GaAs/Si heterostructures grown by molecular beam epitaxy using alloyed AuGe/Ni and non-alloyed Cr/Au contacts. The dark current and optical gain of the Cr/Au devices is higher than that of the AuGe/Ni devices. Contact degradation due to annealing and a p-like background doping consistently explains our data. The gain-optical power relationship follows a power 1aw with an exponent close to -1. PACS numbers: 73.50. Pz, 73.40.Sx, 85.60.Gz The growth of GaAs on Si allows the integration of GaAs devices with the Si technology [1-2]. However, the 4.1% large lattice mismatch results in a high defect density in the epilayer which alters the physical properties of the epilayer and the devices made of it. In this work, we study the dark current and photoresponse properties of planar, interdigitated GaAs/Si photodetection grown by molecular beam epitaxy (MBE). We analyze the effects of contact type, and compare our devices to those fabricated on Cr-doped, semiinsulating (SI) GaAs [3].The Si substrate was (100) p+-type 4° miscut towards [011]. A nominally undoped 2 m layer was first grown by MBE using a twostep method. We applied an unusually high growth rate to enhance growth planarity, and consequently, an epilayer quality [2]: the 50 nm buffer layer was grown with a 5 m/h growth rate at
Single-domain growth of a GaAs layer showing a relatively good crystal structure and specular surface has been demonstrated on a silicon substrate which has been cut along an exact (100) plane. The substrate was patterned with a sawtooth grating using electron beam lithography, and the layers were grown by molecular beam epitaxy.
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