Excimer laser doping techniques for II–VI semiconductors

Excimer laser doping technique has been utilized to obtain a heavy impurity doping in II–IV semiconductors which are considerably difficult materials to achieve bipolar conductivity and to obtain good ohmic contact on them during device fabrication. p-type heavy dopings were examined on CdTe, ZnSe and ZnO using dopant atoms such as Na, K, Sb, or P and diffusing them inside the crystals by irradiating with an excimer laser. Heavily doped layers with the resistivity in the range from 10−2–10−3 Ω cm and the hole concentration of 1017–1018 cm−3 could be obtained. The carrier mobility in those doped p-type layers was in the range from 10–100 cm2/V-s. n-Type doping of CdTe was also investigated using In as a dopant. A highly conductive n-type layer with resistivity, electron concentration and mobility of 5×10−3 Ω cm, 8.9×1018 cm−3 and 140 cm2/V-s, respectively, was successfully obtained. Finally, a CdTe p–i–n diode was fabricated which showed a very good potentiality to be used as a nuclear radiation detector.