Study On CdZnTe Detector Electrode

CdZnTe crystal has proved to be the most excellent material to detect X ray and gamma ray. CdZnTe probe can be widely used in many fields, such as security monitor, industrial flaw-detection, medical diagnosis and celestial body X ray telescope and so on. One of the most key technologies of CdZnTe detector is to make ohmic contact film electrode on CdZnTe crystal's surface. So the main aim of this paper is to deposit all kinds of metal films on CdZnTe crystal in order to find a best ohmic contact electrode, which will establish groundwork for preparing CdZnTe detector. The main research works and results are as follows:Using JGP560 magnetron sputtering machine, Four films(Au,Cu/Ag,Al, Ti) have been deposited on high resistivity CdZnTe semiconductors by DC magnetron sputtering and the contact performances are decided by the I-V curves. As the best ohmic contact electrode in the four films, Au film is studied carefully. Influences of the main depositing parameters on the depositing rates and characteristics of the films are studied systematically. The results show that the sputtering power is the most influencing factor on the depositing rate and the depositing rate increases linearly with the sputtering power increasing;Au film deposited by DC magnetron sputtering has polycrystalline structure;the most compact Au film was deposited under 100W in the power range under research and under 300℃ in the substrate temperature range under research.I-V curves of the Au/CdZnTe specimens are measured with Agilent 4339B high resistivity apparatus and the contact performances are estimated thus. The results show that the contact performance of the film deposited under high sputtering power is better than that of the films deposited under lower power;The contact performance of the film deposited with the substrate temperature being 300℃ is better than that of the films deposited with the substrates being 250℃ and 350℃;The contact performance becomes better after the substrate surface was polished and the contact performance is improved after annealed at suitable temperature.Stress characteristics between CdZnTe substrate and Au film show that the stress of Au film increases with sputtering power and substrate temperature increasing. The stress of Au film decreases with annealing temperature decreasing. Properties of the adhesion of Au films show that the Au films prepared by DC magnetron sputtering all have good adhesion characteristics and increasing sputtering power and substratetemperature has positive effects on the cohesion of the films.