A. S. Tregubova

Electrical characteristics of p-3C-SiC/n-6H-SiC heterojunctions grown by sublimation epitaxy on 6H-SiC substrates

Abstract Sublimation epitaxy in a vacuum (SEV) has been used to obtain p-3C–SiC/n-6H–SiC heteroepitaxial structures. Results of a study of epilayers (X-ray diffraction analysis, scanning electron microscopy involving secondary electrons and electron beam induced current modes) and diode structures on their base ( I – V and C – V characteristics, electroluminescence spectra, DLTS) are presented. Band discontinuities are determined and a band diagram of the p-3C–SiC/n-6H–SiC heterostructure is constructed.

Influence of growth conditions on the structural perfection of β-SiC epitaxial layers fabricated on 6H-SiC substrates by vacuum sublimation

Abstract We report on the influence of the surface quality of substrate, growth rate and vapour phase composition in the growth cell on, both, the size of double position twins (and correspondingly the density of double position boundaries) in β-SiC epitaxial layers and on the perfection of interfacial layers in β-SiC/6H-SiC structures. The growth of β-SiC was done by vacuum sublimation on the (0001)Si-face of 6H-SiC Lely substrates. Epitaxial layers of β-SiC, with 5–6 mm2 double position twins and low (101–102 cm2) defect density, have been grown. The resulting β-SiC/6H-SiC heterostructures had no damaged intermediate layers at the interface.

Investigation of the structure of (p)3C-SiC-(n)6H-SiC heterojunctions

The structure of (p)3C-SiC-(n)6H-SiC epitaxial structures obtained by sublimation epitaxy in vacuum on 6H-SiC substrates was studied by methods of X-ray topography, X-ray diffraction, and transmission electron microscopy. The results showed high structure perfection in the epitaxial layers of both SiC polytypes with a sharp interface between the 3C-SiC and 6H-SiC layers.

Structure and properties of silicon carbide grown on porous substrate by vacuum sublimation epitaxy

A SiC layer was grown by vacuum sublimation epitaxy on porous silicon carbide. A porous SiC layer about 10 µm thick was fabricated by electrochemical etching of an off-axis 6H-SiC substrate. The epitaxial layer was ∼ 10 µm thick. Structural and optical properties of the initial substrate and the porous and epitaxial layers were investigated by X-ray, IR-reflection and photoluminescence methods. An epitaxial SiC layer grown on porous SiC exhibits improved characteristics when compared to a SiC layer on a conventional substrate.

Highly doped p-type 3C–SiC on 6H–SiC substrates

Highly doped p-3C-SiC layers of good crystal perfection have been grown by sublimation epitaxy in vacuum. Analysis of the photoluminescence spectra and temperature dependence of the carrier concentration shows that at least two types of acceptor centers at ∼EV + 0.25 eV and at EV + 0.06-0.07 eV exist in the samples studied. A conclusion is reached that layers of this kind can be used as p-emitters in 3C-SiC devices.

A study of thick 3C-SiC epitaxial layers grown on 6H-SiC substrates by sublimation epitaxy in vacuum

Abstract3C-SiC epitaxial layers with a thickness of up to 100 µm were grown on 6H-SiC hexagonal substrates by sublimation epitaxy in vacuum. The n-type epitaxial layers with the area in the range 0.3–0.5 cm2 and uncompensated donor concentration Nd − Na ∼ (1017–1018) cm−3 were produced at maximum growth rates of up to 200 µm/h. An X-ray analysis demonstrated that the epitaxial layers are composed of the 3C-SiC polytype, without inclusions of other polytypes. The photoluminescence (PL) spectrum of the layers was found to be dominated by the donor-acceptor (Al-N) recombination band peaked at hv ≈ 2.12 eV. The PL spectrum measured at 6 K was analyzed in detail. It is concluded that the epitaxial layers obtained can serve as substrates for 3C-SiC-based electronic devices.

Characterization of p-n structures grown by sublimation heteroepitaxy of 3C-SiC on 6H-SiC

Abstract A study on forward I – V characteristics of p–n structures grown by sublimation heteroepitaxy of 3C-SiC on 6H-SiC shows that about 90% of all the diodes can be placed in two groups. Current–voltage ( I – V ) characteristics of type I diodes are close to those of high-perfection p–n homostructures based on bulk 3C-SiC, with some indications of tunneling currents. I – V characteristics of type II diodes are close to those of p–n homostructures grown by epitaxial methods on single-crystal 6H-SiC substrates. Diodes of both types emit in the entire visible spectral range. The longer-wavelength emission is predominant in type I diodes, and shorter-wavelength emission in type II diodes. However, the main feature of the injection electroluminescence (IEL) is the qualitative similarity of the IEL spectra for diodes of both types. In particular, the IEL spectra of both diode types contain two bands (with hν max ≈2.3 and 2.9 eV), attributed to free exciton annihilation in 3C-SiC and 6H-SiC, respectively.

Structural defects and deep-level centers in 4H-SiC epilayers grown by sublimational epitaxy in vacuum

The parameters of deep-level centers in lightly doped 4H-SiC epilayers grown by sublimational epitaxy and CVD were investigated. Two deep-level centers with activation energies Ec-0.18 eV and Ec-0.65 eV (Z1 center) were observed and tentatively identified with structural defects of the SiC crystal lattice. The Z1 center concentration is shown to fall with decreasing uncompensated donor concentration Nd-Na in the layers. For the same Nd-Na, the Z1 center concentration is lower in layers with a higher dislocation density.

Growth and investigation of the big area Lely-grown substrates

Abstract 6H-SiC substrates grown by Lely method and modified Lely (LM) methods have been studied by X-ray diffractometry and X-ray topography. It has been shown that structural perfection of Lely substrates is significantly higher than that of LM substrates: the former have a dislocation density of 101–103 dis cm−2 (as compared with 103–105 dis cm−2 for latter). Our experiments show that with the use of modernized growth equipment it is possible to obtain Lely substrates with high structural perfection and an area equal to that of LM substrates (1–1.5″ diameter).

Characterization of 3C-SiC/6H-SiC Heterostructures Grown by Vacuum Sublimation

In I-V, EL characterization it was concluded that during the growt h on n-type 6H-SiC substrate of 3C-SiC layer the not intentionally doped regions of p-t ype conductivity formed. It thus appears that two types of pn structures are being formed identifi ed by the polarity of voltage applied to Ni contact on the surface of the epitaxial layer and di splaying different spectra of injection EL. In the EL spectra of the first structure type a peak at h νmax= 2.3 eV is present which, similar to the peak due to free exciton annihilation in 3C-SiC. In the EL spectra of the second structure type two peaks are observed of the same origin as the peaks identified in 6H-SiC pn structures and one more, longer wavelength peak at h νmax between 2.35 and 2.5 eV. TEM revolved that the intermediate layer belongs to 6H polytype. According to EBIC characterization the intermediate layer in studied sample was p-type conductivity. Introduction. Cubic silicon carbide (3C-SiC) is at present a topic of considera ble interest for semiconductor electronics due to the highest charge mobility among all SiC poly types. At certain conditions a growth of α-SiC epilayers on basal orientated substrates of 6H-SiC is a ccompanied by growth of islands of 3C-SiC or transformation of the whole 6H-SiC epilayer into 3C-SiC epilayer. Deposition of 3C layer corresponds to the island growth resulting in double positi on boundaries (DPBs) and stacking fault (SF) formation. Modifying growth conditions in the grow th zone it is possible to obtain various density of DPBs and SF. In recent years, considerable progress has been achieved in the sublimation epitaxy technology. High-quality epitaxial structures of the (n)3C-SiC-(n)6H-SiC type with low densities of DPBs and SF were obtained [1]. The area of n-3C-SiC twin was up to 25 mm. Electrical characteristics of the pn structures were close to those of high perfection pn homostructures based on bulk 3C-SiC [2]. Within the framework of this paper the questions to be discussed will be concerned with epilayer having high density of DPB’s to understand the connection of this defect with electrical characteristics of the structure. Experimental. Epitaxial 3C-SiC layer was grown on 6H-SiC substrate by typical for n-type epitaxy sublimation process in vacuum. Very high density of DPB’s was confirmed by X-ray topography (Fig.1, see also [3]). After that a Ni film was deposited by magnetron sputtering on the surface of the epitaxial layer at 300 C. Ni spots 100microns in diameter were formed by photolitography. Backside ohmic contact (to the Materials Science Forum Online: 2003-09-15 ISSN: 1662-9752, Vols. 433-436, pp 293-296 doi:10.4028/www.scientific.net/MSF.433-436.293