Incorporation and activation of arsenic in MBE-grown HgCdTe

Abstract

Research into P-type doping of HgCdTe with arsenic has concentrated on the use of a conventional effusion cell and optimisation of growth conditions to achieve an increase in incorporation efficiency. This study investigates the use of a cracker cell, which is now the preferred method of doping HgCdTe due to its higher arsenic incorporation efficiency under optimum growth conditions. A detailed investigation of a number of arsenic doped HgCdTe layers grown on CdZnTe substrates by Molecular Beam Epitaxy (MBE) using a cracker cell as a source of arsenic is presented. Growth parameters influencing the amount of arsenic incorporated, such as the cracker-cell bulk temperature and substrate temperature, were investigated. Arsenic depth profiles were obtained via detailed Secondary Ion Mass Spectrometry (SIMS) where all major constituents in the epilayers were analysed. Magneto-transport Hall measurements were performed on as-grown material and those that underwent high temperature anneals typical for arsenic activation. Using the Quantitative Mobility Spectrum Analysis (QMSA) technique, contribution to total conductivity arising by various carriers present in the samples have been separated. As-grown samples were found to exhibit n-type behavior consistent with arsenic incorporating on cation sublattice, while samples that underwent high temperature annealing show partial activation of arsenic with electron compensation.

Arsenic incorporation in MBE‐grown HgCdTe studied with the use of ion milling

“…The n 77 (0), except for films M7 and M8, was in the range of (6-20)×10 15 cm -3 , which exceeded the expected background donor doping N D ((2-3)×10 15 cm -3 [5]). High C As in the films doped at low T cr is explained by higher temperatures of the arsenic source used for the doping of these films [1]. As a result of the annealing, the films doped without cracking were converted into p-type.…”

“…In the as-grown films arsenic is incorporated on cation sites, and a transfer of the As to Te sites is necessary. Defects formed during the growth of Asdoped MCT and during the transfer (activation), which is achieved by a post-growth anneal, are now one of the critical issues in MCT technology [1,2].…”

Hg(1‐x)CdxTe from short to long wave infrared on Si substrates grown by MBE

“…Arsenic doping, on the other hand, has been shown to be sensitive to nearly all growths conditions. Several studies by different groups have reached this same conclusion [14,15]. Figure 3 shows an As SIMS scan for a mid/long wavelength material calibration growth; the growth temperature is kept constant throughout the growth.…”

“…But in contrast to indium, which behaves very well as an n-type dopant, arsenic has amphoteric behavior and with typical MBE HgCdTe growth conditions is incorporated as an n-type dopant. This phenomenon has been seen by other groups and is still a source of discussion [15,[18][19][20][21]. One way to activate the arsenic as a p-type dopant is to anneal the layer under Hg pressure.…”

“…Several works can be found in the literature for As activation [15,[18][19][20][21] and will not be addressed in this work. One of our as-grown LWIR material (x=0.237) obtained by Hall effect measurements shows that the carrier type obtained is n-type and has a concentration of around 1.5x10 15 atoms. This discrepancy can be explained by errors of measurements, ~10% for Hall data and >15% for SIMS [22].…”