50mm×50mm高性能HgCdTe液相外延材料的批生产技术

摘要

采用富碲垂直液相外延技术实现了50mm×50mm×3高性能碲镉汞外延材料的制备.外延工艺的样品架采用了三角柱体结构,并设计了防衬底背面粘液的样品夹具.为保证大面积材料的均匀性,工艺中加强了对母液温度均匀性和组分均匀性的控制,50 mm×50 mm外延材料的组分均方差达到了0.0004,厚度均方差达到了0.4 μ,m.在批量生产技术中,加强了对单轮次生长环境的均匀性和生长轮次之间生长条件一致性的控制,同一轮次生长的3片材料之间的组分偏差小于0.000 4,厚度偏差小于0.1 μm,不同生长轮次之间材料的组分之间的波动在±0.002左右,厚度之间的波动在±2 μm左右.工艺中对碲锌镉衬底的Zn组分、缺陷尺寸和缺陷密度也加强了控制,以控制大面积外延材料的缺陷,晶体双晶衍射半峰宽(FWHM)小于30弧秒,外延材料的位错密度小于1×105 cm-2,表面缺陷密度小于5 cm-2.外延材料经过热处理后,汞空位型的P型Hg0.78Cd0.22Te外延材料77 K温度下的载流子浓度被控制在8 ～ 20×1015cm-3,空穴迁移率大于600 cm2/Vs.材料整体性能和批生产能力已能满足大规模碲镉汞红外焦平面探测器的研制需求.%High performance Hg1-xCdxTe epitaxial materials with the size of 50 mm × 50 mm were produced by Te-rich vertical LPE technology.The sample holder with triangle cylinder structure and a function to prevent HgCdTe solution soaking into the back of the substrates was designed and used to obtain 3 epitaxial materials for each growth process.In order to obtain uniform epilayers,the temperature uniformity and composition uniformity of HgCdTe solution during the process were improved.The STDDEVs for x-value and thickness distributions of 50 mm × 50 mm epitaxial material are 0.000 4 and 0.4 μm,respectively.The average values of x-value and thickness of three epitaxial wafers grown at the same time have a very small difference,less than 0.0004 and 0.1 μm,respectively.The differences of average x-values and thickness values from run-to-run are about ± 0.002 and ± 2 μm,respectively.In order to control the defects of HgCdTe epilayers,the lattice parameters and defects of CdZnTe substrates have been strictly controlled.The full width at half maximum (FWHM) of X-ray double-crystal rocking curve for HgCdTe epilayers was controlled within 30".The dislocation density is less than 1 × 105 cm2,and the surface defect density is less than 5 cm2.Utilizing annealing technique,the carrier concentration of Hg vacancy doped p-type Hg0.78Cd0.22Te epilayers at 77 K were controlled in a range of 8 ～ 20 × 1015 cm3 and their hole mobility exceed 600 cm2/Vs.The material performance and production capacity based on the LPE technique described above can satisfy the demand for fabricating large format HgCdTe infrared focal plane arrays.