Modulation Doping of SiO2 for adjacent Si: Acceptor Candidates (talk)

Doping of deep nanoscale (dns) silicon (Si) for current VLSI technology nodes reached a hard thermodynamic limit: Self-purification and out-diffusion in field effect transistors. Even if dopants manage to enter dns-Si, their ionization energy increases tremendously over values known from bulk Si; no free charge carriers can be provided [1-3]. Modulation doping of III-V semiconductors is used since the late 1970 [4] to achieve excellent electronic and optical material qualities as required for high power LEDs and semiconductor lasers. It took ca. 40 years before the concept was successfully applied to SiO2 as a Si-compatible wide bandgap material [5]. We will introduce criteria for acceptor candidates, showing in the process that a simple roll-over from knowledge about acceptors in Si is very misleading [6]. Since acceptor modulation doping of SiO2 is a fundamental principle, many new properties and applications can be accomplished: Hole-selective contacts for Si-based solar cells with excellent surface passivation [5] by a hitherto undiscovered passivation mechanism [6], very high fixed negative charge densities with good controllability [7], and applications as p-type background doping in VLSI [5].
[1] DOI: 10.1038/srep09702
[2] DOI: 10.1038/s41598-017-08814-0
[3] DOI: 10.3762/bjnano.9.141
[4] DOI: 10.1063/1.90457
[5] DOI: 10.1038/srep46703
[6] DOI: 10.1103/PhysRevApplied.10.054034
[7] DOI: 10.1063/1.5054703
[8] DOI: 10.1021/acsami.8b06098