摘要
制作了反向饱和电流为5.5×10-14A/cm2,势垒高度为1.18eV的GaN肖特基势垒紫外探测器.测量了探测器分别在零偏压及反向偏压下的光谱响应度,响应度随反向偏压无显著变化,零偏压下峰值响应度在波长358.2nm处达到了0.214A/W.利用波长359nm光束横向扫描探测器的光敏面,测量了探测器在不同偏压下的空间响应均匀性,相应偏压下的光响应在光敏面中央范围内响应幅值变化不超过0.6%.光子能量在禁带边沿附近的光束照射下,GaN肖特基势垒紫外探测器存在势垒高度显著降低现象,这种现象在肖特基透明电极边沿及其压焊电极附近表现得更为突出.探测器在368和810nm波长光一起照射时的开路电压比只有368nm光照射时的开路电压大,而零偏压下两者的光电流近似相等.利用这种开路电压变化效应估算了探测器在368nm光照射下,表面被俘获空穴的面密度变化量约为8.4×1010cm-2.
Schottky barrier GaN ultraviolet detectors are fabricated with a very low reverse saturation current density of 5. 5 × 10^14A/cm^2 and very large Schottky barrier height of 1.18eV. The spectral responsivity of the detector at 0V and reverse bias was measured. There are no significant changes in the responsivity at reverse bias voltage. The peak responsivity of the detector at 0V is 0. 214A/W at a wavelength of 358. 2nm. The spatial photoresponse was measured by 359nm light beam scanning across the photosensitive area of the detector at 0V and - 3V. The changes in the photoresponse are no more than 0.6% in the central portion of the photosensitive area at biases of 0V and - 3V. The Schottky barrier height decreases with nearband-edge ultraviolet illumination,especially near the transparent Schottky contact and near the Schottky contact pad. The open circuit voltage of the detector with 368nm light illumination is less than that with both 368 and 810nm light illumination, but the photocurrent of the detector with 368nm light illumination is nearly equal to that with both 368 and 810nm light illumination at 0V. The variation in occupied trap concentration at the GaN surface is estimated to be 8.4 × 10^10 cm^2 by the difference of the open circuit voltage of the detector between cases of illumination with 368nm light and 368nm ＋ 810nm light.
关键词
肖特基势垒
紫外探测器
GaN
开路电压
禁带边
表面态
Schottky barrier
ultraviolet detector
GaN
open circuit voltage, near-band-edge
surface states
