Long-term stability of electron concentration in HgCdTe-based p–n junctions fabricated with ion etching

• Long-term (over 106 min) stability of HgCdTe-based p–n junctions fabricated with ion etching was studied.
• The stability was shown to depend on the growth technique, substrates and doping.
• Indium doping is shown to be a solution for the problem of instability of electron concentration where appropriate.

Results of experimental studies of long-term (∼7 years) stability of electron concentration in HgCdTe-based p–n junctions fabricated with ion etching (IE) are presented. The stability was studied during the storage of ion-etched samples at the room temperature with periodical measurements of carrier concentration and mobility with the use of the Hall effect. It is shown that after ∼103 min after IE electron concentration in un-doped HgCdTe films grown by molecular-beam epitaxy (MBE) on GaAs substrates stabilizes at ∼1015 cm−3 and does not change in 7 years of storage of the films. In contrast to that, in films grown by liquid phase epitaxy and by MBE on Si substrates, electron concentration continues to decrease during all the period of storage and gets lower than 1014 cm−3. For such films, donor doping of the material is recommended, which for indium doping with concentration from 1015 to 1016 cm−3 is shown to be able to keep stable electron concentration for all the studied period of time. In bulk HgCdTe crystal doped with silver, fast re-conversion of the n-region of a p–n junction fabricated with IE back to p-type was observed. The results obtained show some limitations of IE in relation to fabrication of p–n junctions for HgCdTe-based photodetectors, and suggest how these limitations can be avoided.