Defect structure of HgCdTe films grown by molecular beam epitaxy on Si substrates

Abstract

An ion milling-assisted study of defect structure of HgCdTe films grown by molecular beam epitaxy on Si substrates was performed. The films appeared to contain initially neutral Te-related defects with concentration of 10 17 cm −3 , typical of HgCdTe. The concentration of residual donors was found to be quite low ((3-8) × 10 14 cm −3 ). Specific to HgCdTe/Si technology appeared to be a considerable number of stacking faults, which affected the carrier mobility in n-type material. These defects can be annealed in He atmosphere at 230 • C, and after ion milling the electrical parameters of n-type HgCdTe/Si films approach those of high-quality bulk crystals.

Electrical properties of HgCdTe films grown by MOCVD and doped with as

“…Interestingly, however, in samples 1 and 3 the electron mobility extracted with DMSA right after the milling appeared to be higher than that in the as−grown samples. This contrasts these films to other MCT samples studied earlier [10,11,16,19,20], and could be explained by partial de−compensation of the film occurring via Hg vacancy filling and formation of donor complexes comprising As atoms, as described below, along with the relatively low total concentration of donor complexes right after ion milling.…”

“…Also, relaxation data are shown for a nominally un−doped n−type MBE film grown on a GaAs substrate, and a vacancy−doped p−type MBE film grown on a Si substrate. Details on the fabrication of the ISOVPE and MBE films and on the study of their properties with the use of ion mill− ing were given elsewhere [10,11,16,19,20]. Straight after the milling the mobility of the electrons μ n was quite low for the given x values.…”

Defects in HgCdTe grown by molecular beam epitaxy on GaAs substrates

“…The similar effect was observed for HgCdTe/Si, where mobility after annealing, ion milling and relaxation was approaching the upper limit for the given HgCdTe composition. This was explained by suggesting that in the as−grown samples some extra scatter− ing took place on stacking faults (typical of HgCdTe/CdTe/ ZnTe/Si), which were removed by annealing [3]. The absen− ce of stacking faults in HgCdTe/GaAs and a smaller in− crease in mobility after annealing suggest that the post− −anneal increase of μ n observed in this work was caused by decrease in the concentration of compensating acceptors.…”

“…As it was shown for HgCdTe films grown by liq− uid−phase epitaxy, such type of defects may be associated with nano−size Te precipitates that get broken apart by ion milling [6]. Note that the value of n 77 after the milling appeared to depend on x a , which contrasted the films under study to HgCdTe/Si [3]. The dependence of n 77 on x a in the material grown on GaAs is believed to be caused by differ− ent growth conditions (substrate temperatures) used for the MBE of structures with different x a [7].…”

“…At the same time, there is still some lack of understanding of the influence of the specific defect structure of HgCdTe grown by a similar technology on GaAs and Si on the mate− rial electrical properties. In this work, we report on defects in HgCdTe/GaAs films studied using the Hall effect and photoluminescence studies combined with the post−growth treatment (annealing and/or ion milling), and compare the defect structure of n− and p−type HgCdTe/GaAs with those of HgCdTe/Si as reported recently [3].…”