低温处理温度对GaAs光电阴极激活结果的影响

Low Temperature Desorption and Activation of GaAs Photocathode

进行单晶基片和分子束外延(MBE)片两种GaAs(100)光电阴极材料高、低温激活实验,高温处理温度为600℃,低温处理温度分别为580℃、450℃和410℃,阴极每次激活后都利用多信息量测试系统在线测试了其光谱响应曲线。测试结果显示,单晶基片材料在这些温度下的低温激活,灵敏度都比高温提高了30%以上,而MBE外延材料的低温激活结果与低温处理温度有密切关系,在580℃低温处理下,阴极激活后的灵敏度比高温时降低了40.6%,当将低温处理温度降低到450℃,尤其是降低到410℃时,低温激活灵敏度则大幅提高了38.5%,此时阴极长波响应得到大幅提升,光谱响应曲线也最为平坦。分析造成上述现象的原因,可能与两种材料的掺杂元素和低温加热处理特性的不同有关。

The influence of thermal desorption on activation of various types of GaAs photocathode, including GaAs（100） wafer and GaAs films grown by molecular beam epitaxy（MBE）, was experimentally studied. The sample was first heated at high temperature of 600 ℃for 60 minutes,and then thermally desorbed at low temperatures of 580 ℃ ,450 ℃ and 410 ℃ ,respectively. The results show that desorption temperature strongly affects the integral sensitivity of both types of GaAs photocathode. For example, low temperature desorption increases the sensitivity of GaAs wafer by at least 30% .In case of MBE GaAs films,after desorbed at 580 ℃ ,its integral sensitivity decreases by 40.6% ;however, desorption at a temperature lower than 450 ℃, say 410 ℃, increases its sensitivity by 38.5% ; and its long-wavelength response is much stronger with a fairly flat spectral response curve. Possible mechanisms are tentatively discussed.