Quantitative study of the contribution of deep and shallow levels to the compensation mechanisms in annealed InP

Abstract

We have studied the effects of heat treatment under phosphorus atmosphere on the balance of electronic levels by capacitance-voltage and deep level transient spectroscopy measurements. A series of special samples was annealed under the conditions which we are normally using for the processing of nominally undoped semi-insulating (S.I.) InP. It is shown explicitly that in this annealing process the reduction of the free-carrier concentration is predominantly caused by a reduction of the net concentration of defects related to shallow levels. Furthermore, we have identified in the annealed material two defects related to electron traps with activation energies of 400 and 600 meV, which are created or incorporated during the annealing with limited concentrations of about (0.5–1)×1015 cm−3. On the basis of these results we conclude that for the compensation mechanism in the annealed nominally undoped S.I. InP only a concentration below 1015 cm−3 of defects with a midgap energy level is necessary.

Traps in undoped semi-insulating InP obtained by high temperature annealing

“…15,16 Hirt et al have observed, by DLTS, in annealed but still conducting undoped InP, an electron trap having the same activation energy ͑0.4 eV͒ whose concentration increases with phosphorus pressure. 8,10 They as well observe in both undoped and Fe-doped annealed SI InP the same level by TSC. 10 In addition Zerrai et al 17 have reported the presence of a level named P3 having an activation energy ranging from 0.35 to 0.40 eV in Fe-doped SI InP and show that its concentration is not affected by the amount of Fe.…”

“…observed. 23 They suggest that it could be due to a contamination during the annealing process. In our samples, the level at 0.6 eV is observed with a low concentration as compared to the other defects.…”

“…Hofmann et al 3 have been the first to get real semiinsulating state for InP ͑Ͼ10 7 ⍀ cm͒ by annealing under phosphorus ambiance. This has been reproduced in Japan by Kainosho et al 4 and then has given place to several studies [5][6][7][8][9][10][11] to understand the physical phenomena involved in the compensation mechanism. At present time a general model 11 assumes that an annihilation of intrinsic defects related to donors occurs due to the annealing in phosphorus ambiance.…”

Thermally induced conduction type conversion in n-type InP

“…[1][2][3][4][5] Generally, thermally induced defects in the annealed material can be detected by different spectroscopy methods. [6][7][8] However, most of the reports so far 4-8 ͑including our previous work͒, 9 have been carried out in a single annealing run with high temperature and long duration. The defects in the material can only be detected in their final thermodynamic equilibrium states after long time annealing.…”

Semi-insulating InP through wafer annealing

“…This implies clearly that wafer annealing at lower temperatures has an effect in reducing phosphorus vacancies. The mechanism of SI behavior has been extensively studied by various methods such as Mall effect [ 111,TSC[33], DLTS [34,35] and PL measurements [13,14]. The following three mechanisms have been proposed.…”