SiC Photodiode Wafer *S

SiC is widely used in the construction of ultraviolet (UV) photodetectors due to its wide bandgap (~3.2eV), excellent thermal conductivity, and excellent radiation resistance. These excellent performances enable SiC based ultraviolet photodetectors to be applied in environments with chemical inertness, high temperatures, and strong radiation. p-i-n photodiodes, avalanche photodiodes (APDs), and Schottky-type photodiodes are the most common SiC photodetectors. PAM-XIAMEN is able to manufacture SiC photodiode wafers for fabricating Schottky type, p-i-n and APD photodetector, with specific parameters as follows:

1. SiC Based Photodiode Epiwafers

1) 4H-SiC Schottky Photodiode Epi-Structure

Epi	Thickness	Doping level
n- epilayer	–	4.25×1015cm-3
n+ SiC substrate

 

2) 4H-SiC Based p-i-n Photodiode Epi Structure

Epi	Thickness	Doping level
p+ layer	–	–
i layer	–	–
n layer	–	2×1018cm-3
4H-SiC substrate

 

3) SiC Avalanche Photodiode Epiwafer Structure

Epi	Thickness	Doping level
P+ layer	–	5×1019cm-3
n layer	–	–
n- layer （intrinsic layer）	–	–
n layer	1000nm	–
n+ SiC substrate

 

2. About Schottky, p-i-n, and APD Structured SiC Photodiode

Schottky type SiC UV photodiode: they are widely used due to their simple structure, relatively easy preparation process, and suitability for devices and arrays with large photosensitive areas. For many years, the development of Schottky structured 4H-SiC UV photodiodes has mainly focused on the optimization of processes and electrodes, as well as the study of device reliability.

SiC p-i-n photodiode: the active region of the p-i-n structure silicon carbide photodiode is designed to be separated from the surface, which can be made thicker and beneficial for improving the quantum efficiency of the device. Due to the pn junction of the p-i-n structure in the bulk material, its dark current is low, and the junction capacitance of the device is also small, resulting in a fast response speed. Therefore, the three main parameters of the photodetector (dark current, responsivity, and response speed) are relatively good. The p-i-n structure is currently the most optimized structure for photodetectors and the main structural form of UV photodetectors with high UV detection sensitivity.

The SiC p-i-n photodiode structure has two main means of p-layer formation: one is through epitaxial growth, and the other is through ion implantation. The p-layer grown by epitaxy has good quality and fewer defects, but can only grow on a large area as a whole layer, making it impossible to prepare complex structured selective doping; Ion implantation can form a p-layer in local areas, which is more flexible and suitable for preparing complex structured devices. However, due to the lattice damage caused by ion implantation, it can to some extent reduce device performance.

SiC APD: Due to its internal gain, the SiC APD structure not only requires a large difference in ionization rates between material electrons and holes, but also demands strict device structures, otherwise it will cause avalanche noise. At the same time, the preparation process of APD structure ultraviolet photodiodes is more complex than other structures.

At present, compared with other 4H SiC photodetectors, 4H SiC APD is the only UV photodetector with high internal gain and broad application prospects. The 4H SiC APD structure mainly includes p-i-n structure, separate absorption layer and multiplier layer (SAM) structure, and separate absorption charge multiplier layer (SACM) structure. The development of APD mainly revolves around two aspects. On the one hand, it aims to optimize the device preparation process and structure, suppress edge breakdown, improve avalanche gain, and reduce avalanche breakdown voltage, so that the device can work better in an avalanche state; On the other hand, single photon imaging is achieved using APD arrays.

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