Ultra wide band CW THz wave generation with ultra narrow line width

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Layered semiconductor crystal GaSe was grown for the first time by using our original liquid phase method at low and constant growth temperature. Due to the low growth temperature, pure single epsilon phase crystals can be realized. It is shown that the stoichiometry control improved the IR and THz absorption characteristics. From the electrical evaluation results, it is noticed that the our liquid phase grown crystals contain less native point defects compared with those in commercially available Bridgman grown crystals. In order to reduce the free carrier absorption, transition element impurity was doped and then deep levels can be introduced in the band gap, as expected. By using our liquid phase grown crystals, THz generation was realized with the output power up to about 3mW. It is shown that the generation efficiency was improved by one order of magnitude compared with that of commercially available Bridgman grown crystals.