Performance improvement of large area GaN MSM photodiode with thin AlGaN surface layer
Performance improvement of large area GaN MSM photodiode with thin AlGaN surface layer
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DOI：
10.1108/13565361011061939
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发表时间：
2010-01-01
影响因子：
1.1
通讯作者：
Abu Hassan, H.
中科院分区：
文献类型：
--
作者：
Chuah, L. S.;Hassan, Z.;Abu Hassan, H.
目的-本文的目的是提出一种基于GaN的金属-半导体-金属（MSM）光电二极管的新结构，其中在常规的Si上GaN（111）器件结构上添加薄的非故意掺杂的n型AlGaN层。在GaN MSM光电二极管中引入了100 nm的（0.50）Ga（0.50）N帽层，以提高有效肖特基势垒高度并降低暗电流。当光子能量高于GaN带边但低于AlGaN带隙的入射光照射到光电二极管正面时，光在顶部AlGaN层中可以透明，只被GaN层吸收。结果表明，AlGaN/GaN界面态对GaN层中的光生载流子有影响。由于界面态的密度通常低于表面态的密度，因此光生电子-空穴对的复合会减少。正常GaN MSM光电二极管的0.54 eV的势垒高度增加到0.60 eV的有效势垒高度。结果-所得MSM光电二极管在5 V偏压下显示出低至8.0 x 10（-4）A的暗电流，这比普通GaN低大约两个数量级（1.0 × 10（-2）在5V偏置）MSM光电二极管。独创性/价值-该文件的势垒增强GaN肖特基MSM光电二极管使用薄AlGaN帽层的报告。发现AlGaN帽层有效地抑制GaN肖特基MSM光电二极管的漏电流，从而改善器件特性。与AlGaN盖层的肖特基接触的暗电流被示出为比常规GaN肖特基MSM光电二极管的暗电流小约两个数量级。
Purpose - The purpose of this paper is to propose a new structure of GaN based metal-semiconductor-metal (MSM) photodiode, in which a thin unintentionally doped n-type AlGaN layer is added on the conventional GaN on Si(111) device structure.Design/methodology/approach - A thin Al(0.50)Ga(0.50)N cap layer of 100 nm was incorporated in GaN MSM photodiode to enhance the effective Schottky barrier height and reduce the dark current. When the incident light with photon energy higher than the band edge of GaN but lower than the bandgap of AlGaN illuminates the front face of photodiode, the light can be transparent in the top AlGaN layer and is only absorbed by the GaN layer. As a result, the photogenerated carriers in the GaN layer would be influenced by the interface states of AlGaN/GaN. It is known that the density of the interface states is normally lower than that of surface states, so the recombination of photogenerated electron-hole pairs will be reduced. A barrier height of 0.54 eV for normal GaN MSM photodiode was increased to the effective barrier height of 0.60 eV.Findings - The resulting MSM photodiode shows a dark current of as low as 8.0 x 10(-4)A at 5 V bias, which is about two orders of magnitude lower than that of normal GaN (1.0 x 10(-2)A at 5V bias) MSM photodiode.Originality/value - The paper reports on barrier enhanced GaN Schottky MSM photodiode using a thin AlGaN cap layer. AlGaN cap layers were found to effectively suppress the leakage current of the GaN Schottky MSM photodiode, resulting in improved device characteristics. The dark current for the Schottky contact with the AlGaN cap layer was shown to be about about two orders of magnitude smaller than that of conventional GaN Schottky MSM photodiode.