Field enhanced GaN photocathode and a proposed implementation method

Varied p-type doping structure has been verified to be efficient to improve the QE of III-V semiconductor photocathode because of the built-in electric field, and the gradient-doping structure is also efficient for GaN photocathode. Here we study the band structure of the exponential-doping GaN photocathode and get the QE formula. Based on the formula, the parameters influencing the QE are analyzed. Due to the limitation of MOCVD method, it is hard to obtain exponential-doping structure GaN photocathode. Here ALD method is proposed to grow exponential-doping GaN material, TMG, NH3, and Cp2Mg are chosen as the Ga, N, and Mg precursor source, respectively. Growth temperature is fixed at the range of 450-550 °C, and within this temperature range crystal structure GaN material can be obtained. Finally, to get the exponential-doping structure, the relationship of Ga and Mg cycle is studied, and the formula is given.