摘要
采用GaSb体材料和InAs/GaSb超晶格分别作为短波与中波吸收材料,外延生长制备了NIPPIN型短中双色红外探测器。HRXRD及AFM测试表明,InAs/GaSb超晶格零级峰和GaSb峰半峰宽FWHM分别为17.57 arcsec和19.15 arcsec,范围表面均方根粗糙度为1.82。77 K下,SiO2钝化器件最大阻抗与面积乘积值RA为,暗电流密度为,侧壁电阻率为。经阳极硫化后,器件最大值为,暗电流密度为,侧壁电阻率为。相同偏压下,硫化工艺使器件暗电流降低1-2个数量级,侧壁电阻率提高了1个数量级。对硫化器件进行了光谱响应测试,器件具有依赖偏压极性的低串扰双色探测性能,其短波通道与中波通道的50%截止波长分别为1.55 和4.62 ,在1.44 、2.7 和4 处,响应度分别为0.415 A/W、0.435 A/W和0.337 A/W。
双色红外探测器具有探测波段范围广、特征信息丰富、分辨能力强、抗干扰等优点,在国内外一直是红外探测与成像领域的热
本文在N型GaSb衬底上,采用分子束外延技术生长了基于InAs/GaSb超晶格和GaSb体材料的中短波双色红外探测器,并采用背靠背的NIPPIN型双二极管结构。通过刻蚀、硫化、钝化后获得双色单元探测器件,由于采用了新结构,因此主要分析了其晶体结构、表面形貌、器件IV特性和表面漏电流,并对红外光谱进行了简要分析。
样品外延在采用固体源的Veeco Gen-Ⅱ分子束外延系统的生长室内进行,此设备的As2和Sb2为裂解源,衬底为N型GaSb(001)衬底。如

图1 InAs/GaSb超晶格/GaSb体材料中短波双色红外探测器结构图
Fig. 1 Structure diagram of mid-/short-wave dual-band infrared detector based on InAs/GaSb superlattice/GaSb bulk material
器件工艺过程主要包括

图2 工艺流程示意图
Fig. 2 Schematic diagram of process flow
因有文章指出硫化会对材料表面及侧壁造成损伤且时效短不稳

图3 器件垂直剖面结构示意图(a)阳极硫化+钝化,(b)直接SiO2钝化
Fig. 3 Schematic diagram of device vertical profile (a) Anodic sulfuration+passivation, (b) direct SiO2 passivation
本文中高分辨率X射线衍射(HRXRD)仪为Jordan Valley JV-QC3 X型,使用波长为1.54 Å的Cu 辐射,以-2方式扫描,用于检测超晶格周期厚度、材料应变等信息;原子力显微镜(AFM)为NanoScape Ⅲ a(Digital Instruments)型,工作方式为非接触式,对样品无损伤,横向与纵向分辨率分别为1.5 nm和0.05 nm,达到原子级;扫描电子显微镜(SEM)型号为Nove Nanosem 650,用于观察器件侧壁形貌;暗电流测试使用CRX-4K低温探针台,安捷伦B1500A半导体设备分析仪,测试温度范围可由7 K至300 K;红外光谱测试使用Vertex-70傅里叶变换红外光谱仪(FTIR),其可覆盖远红外(15 c

图4 样品的高分辨率X射线衍射(HRXRD)图像
Fig. 4 High-resolution X-ray diffraction (HRXRD) image of the device
采用原子力显微镜和扫描电镜对样品的表面形貌、表面粗糙度及截面形貌进行了测试,如



图5 样品表面光学显微镜图像(a)、表面AFM图像(b)和截面SEM图像(c)
Fig. 5 Optical microscope image of the sample surface (a) AFM image of the surface (b) and SEM image of the section(c)
本文比较了单纯SiO2钝化和阳极硫化+SiO2钝化工艺对直径为200 器件性能的影响,在不同温度(77 K、90 K、110 K、130 K、150 K、170 K、190 K、210 K、230 K)下测试了暗电流密度和阻抗面积乘积值RA随偏压的变化曲线,如

图6 不同温度下器件的暗电流密度和RA随偏压的变化曲线,(a)、(c)为硫化+SiO2钝化器件,(b)、(d)为SiO2钝化器件
Fig. 6 Curve of dark current density J and R∙A at different temperatures vs bias for sulfurized +SiO2 passivated devices (a) and (c) and SiO2 passivated devices (b) and (d)
为了更直观地观察两组器件性能随温度的变化情况,绘制了在-100 mV偏压下两组器件性能随温度的变化情况,如

图7 -100 mV偏压下器件暗电流密度(a)和RA值(b)随温度变化的曲线
Fig. 7 Curves of the dark current density (a) and R∙A value (b) of the device varying with temperature under bias voltage of -100 mV
, | (1) |
式中,与总暗电流相关,等式右边第一项()Bulk与体漏电流相关,第二项与表面漏电流相关,其中 为侧壁电阻率,其值越大,表明表面漏电流越小。

图8 77K不同台面面积器件的随P/A值变化的数据及其拟合曲线
Fig.8 The data of R0A changing with P/A value of devices with different mesa area at 77 K and its fitting curve
为了验证该探测器的双色探测性能,在77 K和不同偏压下对硫化器件进行了光谱响应测试。

图9 77 K器件的归一化光谱响应曲线 (a)正偏-短波通道, (b)反偏-中波通道
Fig. 9 Normalized spectral response curve of the device (a)short wave channel, (b)middle wave channel
利用标准DTGS探测器和500黑体在77 K下对无减反膜的硫化器件响应光谱进行校准,获得器件的响应度如

图10 黑体校准后的器件响应度曲线
Fig. 10 Blackbody spectral responsivity curve of the device
外延生长并制备了基于InAs/GaSb超晶格和GaSb体材料的NIPPIN型中短波双色红外探测器。超晶格零级卫星峰和GaSb峰的半峰宽FWHM分别为17.57 arcsec和19.15 arcsec,范围内样品表面均方根粗糙度RMS为1.82,表明材料有极高的外延质量。对器件进行了硫化与钝化对比,77 K下硫化和SiO2钝化器件的最高阻抗分别为和,不同温度和台面尺寸的I-V测试得到硫化和钝化器件侧壁电阻率分别为和,表明硫化可有效减少侧壁表面漏电流,提升器件性能。对硫化器件进行了光谱响应测试,短波通道与中波通道的50%截止波长分别为1.55 和4.62 ,峰值响应度分别为1.44 处的0.415 A/W和2.7 处的0.435 A/W,中波通道在4 处响应度为0.337 A/W。此器件在未采取势垒层,而是采取较大的掺杂和接触层厚度提高势垒的情况下,可通过偏压调制实现低串扰的中短波双色红外探测,且结构简单无需组分调整可重复性强。
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