Preparation of SiC/Ge/graphene heterostructure on 4H-SiC(0001)

Highlights

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SiC/Ge/graphene heterostructure on 4H-SiC was employed to realize VIS-NIR light operation of SiC devices.

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Self-assembled submicron Ge islands have been prepared on 4H-SiC(0001) successfully.

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Graphene on Cu foil was grown and wet transferred on Ge islands to form SiC/Ge/graphene heterostructure.

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The structure of the SiC/Ge/graphene heterojunction is defined by XRD, TEM and Raman spectra characterizations.

Abstract

Due to the wide bandgap of SiC, SiC-based optoelectronic devices can not be operated by visible (VIS) and near-infrared (NIR) light sources. A promising way to solve this problem is to adopt a SiC/Ge/Graphene heterostructure. The Ge film can be used as VIS-NIR-absorbing layer. As a electrode, graphene also forms a Schottky junction with Ge on 4H-SiC. To form the SiC/Ge/graphene heterostructures, Ge film was prepared on 4H-SiC(0001) by chemical vapor deposition, and then graphene on Cu foil was wet transferred on Ge films. The Ge film on 4H-SiC(0001) has polycrystalline structure and consists of self-assembled submicron Ge islands. The monolayer graphene with a few cracks and wrinkles was transferred on the Ge rough surface. The SiC/Ge/graphene heterostructure with high light absorption in the 500–1200 nm range was prepared on 4H-SiC successfully.

Graphical abstract

Keywords

SiC;

Ge/graphene; heterostructure 

Raman

Microstructure;

Chemical vapour deposition;

Source:ScienceDirect

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Fundamental Summary of LED SiC Substrate

Silicon carbide is also called "emery powder" or "refractory sand." The usual manufacturing process of SiC is to combine silica sand, tar (or coke), woodchip (and salt when manufacturing green SiC) and other materials in an electric resistance furnace at a high temperature. Silicon carbide is usually divided into two categories, the black SiC and the green SiC, both having a hexagonal crystal structure, a density of 3.2 -3.25g/cm³ and microhardness of 2840-3320kg/mm2. The black SiC is manufactured with silica sand, tar and high quality silica as main materials in an electric resistance furnace at a high temperature. It is of hardness between corundum and diamond, mechanical robustness higher than corundum, crisp and sharp. The green SiC is manufactured with tar and high quality silica as main material, salt as additive, and in an electric resistance furnace at a high temperature. The hardness of green SiC is also between corundum and diamond, and mechanical robustness is higher than corundum.

Silicon carbide is of high hardness, good thermal and electrical conductivity, and is oxidation resistant under high temperature. It can be used as abrasive material or be made into abrasive tools such as abrasive wheel, sharpening stone, grinding unit, abrasive segment and so on. It can also be used as high temperature material and deoxidant in metallurgy. There are four major fields where silicon carbide is in general application: functional ceramics, high grade refractory, abrasive and metallurgy materials. And high-purity silicon carbide can further be used in semi-conductor and silicon carbide fibre production. Due to its unique physical and electrical properties, silicon carbide has become the best semi-conductor in some applications such as short wavelength photoelectric cell, high temperature, radiation resistant element and high frequency, high power component. Its major advantages are as following:

1.Wide energy level(eV)

 4H-SiC: 3.26 6H-Sic: 3.03 GaAs: 1.43 Si: 1.12

2.High thermal conduct efficiency(W/cm‧K@RT)

4H-SiC: 3.0-3.8 6H-SiC: 3.0-3.8 GaAs: 0.5 Si: 1.5

3.High disruptive field intensity

4H-SiC: 2.2x106 6H-SiC: 2.4x106 GaAs: 3x105 Si: 2.5x105

4.High saturated electron drift velocity(cm/sec @E 2x105V/cm)

4H-SiC: 2.0x107 6H-SiC: 2.0x107 GaAs: 1.0x10 Si: 1.0x107

With its wide energy level, the electronic components made of SiC are able to work under extremely high temperatures, can resist voltage and electric field 7 times larger than silicon and gallium arsenide, and is therefore especially good material in manufacturing high pressure and high power components, like high pressure diode. In addition, SiC is good thermal conductor with better conductivity than any other semi-conduct materials. These excellent characteristics have made SiC widely used in both industry and military fields.

Keywords:LED Substrate,

Source:LEDinside

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Combining graphene with silicon carbide: synthesis and properties – a review

Abstract

Being a true two-dimensional crystal, graphene possesses a lot of exotic properties that would enable unique applications. Integration of graphene with inorganic semiconductors, e.g. silicon carbide (SiC) promotes the birth of a class of hybrid materials which are highly promising for development of novel operations, since they combine the best properties of two counterparts in the frame of one hybrid platform. As a specific heterostructure, graphene on SiC performs strongly, dependent on the synthesis method and the growth modes. In this article, a comprehensive review of the most relevant studies of graphene growth methods and mechanisms on SiC substrates has been carried out. The aim is to elucidate the basic physical processes that are responsible for the formation of graphene on SiC. First, an introduction is made covering some intriguing and not so often discussed properties of graphene. Then, we focus on integration of graphene with SiC, which is facilitated by the nature of SiC to assume graphitization. Concerning the synthesis methods, we discuss thermal decomposition of SiC, chemical vapor deposition and molecular beam epitaxy, stressing that the first technique is the most common one when SiC substrates are used. In addition, we briefly appraise graphene synthesis via metal mediated carbon segregation. We address in detail the main aspects of the substrate effect, such as substrate face polarity, off-cut, kind of polytype and nonpolar surfaces on the growth of graphene layers. A comparison of graphene grown on the polar faces is made. In particular, growth of graphene on Si-face SiC is critically analyzed concerning growth kinetics and growth mechanisms taking into account the specific characteristics of SiC (0001) surfaces, such as the step-terrace structure and the unavoidable surface reconstruction upon heating. In all subtopics obstacles and solutions are featured. We complete the review with a short summary and concluding remarks.

Source:IOPscience

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