锑化物超晶格长波红外焦平面探测器研究进展

Progress of long wavelength infrared focal plane arrays based on antimonide compounds superlattice

锑化物的研究开始于20世纪50年代,70年代随着超晶格概念及后来能带工程的出现,锑化物在红外探测领域的潜力逐渐显露.基于现实的需求,锑化物材料的生长外延及工艺处理技术取得了快速进步,这也得益于之前对Ⅲ-Ⅴ族材料的大量研究.Ⅱ类超晶格(T2SL)的发展主要源于两个主要原因:首先相对于HgCdTe材料,Ⅱ类超晶格具有低成本、可重复性、可操作性、高均匀性等优势,尤其在长波红外及以上波段,Ⅱ类超晶格相对于HgCdTe的优势更明显.其次与HgCdTe材料相比,Ⅱ类超晶格具有很低的俄歇复合概率,这意味着Ⅱ类超晶格红外探测器具有比HgCdTe探测器更低的暗电流或更高的工作温度,提高长波焦平面的工作温度对于降低成像系统的功耗、尺寸及重量至关重要.另外,大气窗口在8–14μm有最高的透射率,同时温度为室温(300 K)的物体所发射的红外辐射波长大约为10μm.因此,长波红外探测对于InAs/GaSbⅡ类超晶格极具价值.理论上Ⅱ类超晶格红外探测器在等效截止波长下能提供同等或超越HgCdTe探测器的性能.但由于Ⅱ类超晶格材料在少子寿命上与HgCdTe存在很大差距,导致Ⅱ类超晶格探测器在耗尽区有很高的产生复合电流.为了抑制产生复合电流及其他机制暗电流,提出了各种结构并应用于Ⅱ类超晶红外探测器上,如PπMN结构、CBIRD以及单极势垒型等,极大地降低了长波器件的暗电流,同时增加了器件阻抗及探测率.此外,InAs/InAsSb超晶格的提出,避免了由Ga在禁带引入复合中心,有效地提高了少子寿命.随着Ⅱ类超晶格技术及理论的不断完善,锑化物超晶格长波焦平面在可操作性、均匀性、稳定性、可扩展性上的优势将更为明显.

The research of antimonide compounds began with 1950s.With the appearing of superlattice concept and energy band engineering in the 1970s,the potentials in infrared detection of antimonide compounds gradually emerged.Due to the reality demand,epitaxy and preparation technologies of antimonide-based materials have achieved rapid progress.The rapid advance of T2SL also benefits from the previously five decades ago of development of Ⅲ-Ⅴ group materials and devices research.The development of In As/Ga Sb type-Ⅱ superlattices (T2SLs) results from two primary motivations:the In As/GaSb superlattice has more apparent advantages than HgCdTe in low cost,reproducibility,operability and high uniformity,especially for long wavelength detector.Secondly,the Auger recombination probability of type Ⅱ superlattices is lower than that of HgCdTe,which means that the infrared detector of type Ⅱ superlattice has a lower dark current or a higher working temperature than that of HgCdTe detector.And improving the working temperature of the long-wave focal plane is crucial for reducing the power consumption,size and weight of the imaging system.In addition,the atmosphere window with highest transmittance is located at the range of 8-14μm.And the emitted infrared radiation by an object at room temperature (300 K) has a wavelength of about 10μm.Therefore,long wavelength infrared detection is extremely valuable for In As/Ga Sb type-Ⅱ superlattices.Compared with HgCdTe device,T2SL detectors can provide equivalent or better performance under the same cutoff wavelength.But the short minority carrier lifetime of In As/Ga Sb superlattice cause a high level of generation-recombination current (Jgr).In order to suppress Jgrand other dark current,the different device structures like W-structure,PπMN structure,CBIRD and unipolar barrier were put forward and employed in the detectors.As a result,the dark current and impedance was greatly improved.Furthermore,with the putting forward of In As/In As Sb superlattice,the defects level in band gap introduced by Ga were avoided,and the minority carriers lifetime were effectively improved.The reproducibility,operability and uniformity of T2SL bring more advantages than HgCdTe detector with the sustainable developement of T2SL technologies and theories.