Atomic layer deposition of p-type semiconducting thin films: a review

Semiconductors such as elemental silicon allowing both p-type and n-type doping are the backbone of the current microelectronics industry, while the continuous progress in fabrication techniques has been the key for ever-increasing integration density and device miniaturization. Similarly, in the strongly emerging field of transparent electronics both p-type and n-type compound semiconductors are needed that moreover should be transparent within the entire visible spectral range. Atomic layer deposition (ALD) has been the thin-film deposition method of choice for a number of challenging applications in microelectronics, and it would also be a highly relevant technology for transparent electronics. Currently the appropriate p-type semiconducting compounds are far outnumbered by the n-type compounds. Hence there is an obvious search for high-quality thin films of new p-type compound semiconductors. This is clearly seen in the increasing number of ALD papers published annualy on p-type semiconducting materials. In this overview the current state of research in the field is briefly presented; the ALD processes so far developed for the various p-type (transparent) conducting material candidates are summarized, and the most prominent electrical transport and optical properties achieved for these thin films are highlighted.