SiC material has high displacement threshold energy and wide band gap, which enables the detector to work under high temperature and high radiation field. It can be applied to neutron fluence/energy spectrum measurement in strong radiation field, neutron fluence/energy spectrum measurement in high temperature environment, reactor power monitoring, radiation monitoring of spent fuel storage sites, D-T neutron tube beam current monitoring, pulsed neutron. The detector fabricated on SiC epitaxial thin film can also be used in the fields of uranium mine logging, nuclear medicine and neutron photography, in the field of charged particle and neutron measurement under high temperature and high radiation environment in space, and can be used as a vertex and track detector for high-energy physics experiments. Therein, PAM-XIAMEN can supply SiC epitaxial structure to manufacture thin SiC epitaxial detector for measurement heavy ions and charged particles. More details on the SiC epitaxial wafer, please check out the following:
1. Specification of SiC Epitaxial Thin Film
Type: n type/N doped
Diameter: Ø4” (±0.1mm)
Thickness: 350(±25) µm
Surface: both sides polished
Si face epi-polished, Ra<0.5nm
C-face polished, Ra<3.0nm
Primary flat: (10-10) ±0.5°
Secondary flat: necessary flat to be provided for surface identification
Laser mark: c-face
Useable area: >/= 90%
Thickness: 20um+/-5%um, n type
Dopant: N atom 1E15cm-3+/-25%
The low-resistivity SiC substrates will be removed by HF anodic dissolution. For this reasons the resistivity of epitaxial SiC layer should be as high as possible and resistivity of SiC substrate should be as low as possible.
So, to deal with this problem, we will try to choose lower resistivity substrate around 0.02 ohm.cm, and epi layer in low concentration to higher the resistivity around 13 ohm.cm during the epitaxial growth of silicon carbide.
2. Requirements of High-Performance Detector for Epitaxial Growth of SiC Thin Films
To make high performance detector, the quality of SiC single crystalline epitaxial thin film growth should meet following requirements:
1) Few defects and good uniformity of SiC substrate and epitaxial layer;
2) Smaller reverse leakage current and higher reverse bias voltage;
3) Larger thickness of the detector sensitive area;
4) A low density of surface states on SiC.
3. Requirements for Metal Electrodes of Detectors on SiC Epitaxial Thin Film
The requirements of SiC detectors for metal electrodes are mainly:
Ohmic contact: Low specific contact resistivity and high stability;
Schottky contact: There is a large Schottky barrier height, and the barrier distribution is uniform.
3.1 Ohmic Contact
For n-type 4H-SiC semiconductor material, to form ohmic contact, the electrode material needs to be a metal with low work function that satisfies the condition of Φm<Φs, while 4H-SiC has a large forbidden band width (3.26eV), and the electron affinity is only 3.1eV, and the work function of most metals is 5-6 eV, it is difficult to find low work function metals that meet the conditions, and the metal/SiC contact generally exhibits rectification characteristics.
The current method for preparing n-type SiC ohmic contact is to use metal and heavily doped (>1*1018 cm-3) SiC contact to anneal at high temperature (>950 °C). The formation of interfacial silicide at high temperature can overcome the influence of SiC epitaxial thin film surface properties on contact properties.
3.2 Schottky Contact
Schottky contacts are fabricated by depositing metal on a SiC epitaxial layer. A good Schottky contact requires a large Schottky barrier height. For n-type SiC epitaxial thin film process, Schottky contacts require lower doping concentrations, typically lightly doped (<1015).