指数掺杂反射式GaSb光电阴极表面光电压谱研究

通过求解一维少数载流子扩散方程,对反射式GaSb光电阴极表面光电压谱理论公式进行了研究。利用MOCVD外延生长掺杂结构不同、吸收层厚度相同的两种阴极材料,通过MIS法表面光电压谱测试和理论拟合发现,指数掺杂结构在后界面符合速率和吸收层厚度相同的情况下能够有效提高GaSb阴极少子扩散长度,主要原因是指数掺杂形成的内建电场有助于光生电子以电场漂移的方式向吸收层表面运动,从而提升GaSb光电阴极的光电发射效率和表面光电压谱。

The theoretical formula of photovoltage spectrum on the surface of reflective GaSb photocathode is studied by solvingthe one-dimensional minority carrier diffusion equation. Two kinds of cathode materials with different doping structure and the samethickness of absorption layer were grown by MOCVD epitaxy. The results of surface photovoltage spectrum measurement and theoretical fitting by MIS method were found. The exponentially doped structure can effectively increase the minority carrier diffusion lengthof the GaSb cathode under the condition that the posterior interface accords with the rate and the thickness of the absorption layer isthe same. The main reason is that the built-in electric field formed by exponentially doped helps photogenerated electrons move tothe absorption layer surface in the way of electric field drift, thus improving the photoemission efficiency and surface photovoltagespectrum of GaSb photocathode.