Annealing of defect density and excess currents in Si-based tunnel diodes grown by low-temperature molecular-beam epitaxy

Abstract

Deep-level transient spectroscopy ͑DLTS͒ measurements were performed in order to investigate the effects of post-growth heat treatment on deep level defects in Si layers grown by low-temperature molecular-beam epitaxy ͑LT-MBE͒ at 320°C. In the LT-MBE as-grown samples, two dominant divacancy-related complex defects, of which the possible origins are suggested as P-V (E center)ϩV-V (0/Ϫ) and V-V (Ϫ2/Ϫ) and others, were observed in P-doped n layers. When the as-grown samples were annealed at 700, 800, and 900°C for 60 s by rapid thermal annealing, the total density of defects were decreased without generating other defects and most defects were annihilated at 900°C. This study also compared the DLTS trends with performance of Si-based resonant interband tunnel diodes ͑RITDs͒ in terms of peak current density, valley current density, and peak-to-valley current ratio, which are closely related to the deep-level defects. The active regions of the RITDs were grown at the same substrate growth temperature and annealed at similar temperatures used in this DLTS study.

Effect of temperature on layer separation by plasma hydrogenation

“…23,24 The net effect of vacancies during hydrogenation is to act as traps that mediate the diffusion of H, which in turn decreases the H flux at the strain layer. However, the stability of H related vacancy defects or pure vacancy defects are temperature dependent.…”

Observation of strain in pseudomorphic Si1−xGex by tracking phonon participation in Si∕SiGe resonant interband tunnel diodes via electron tunneling spectroscopy

“…The reduced substrate temperature limits the ability of surface adatoms to move in a correlated manner to a step edge, creating vacancy-type defects. 28,29 The addition of increasing amounts of Ge to the central spacer certainly lowers the tunneling barrier as the effective composite bandgap E g of the RITD tunneling spacer reduces and also shrinks the effective mass m * , thereby greatly increasing the tunneling probability and associated tunneling current density, as shown in Eq. ͑6͒ below from Kane's model, 34,35 J t ϰ q 2 36ប 2 ͱ 2m * E g expͩ− 4 ͱ 2m * E g 3/2 3qប ͪ.…”

“…A postgrowth rapid thermal annealing at 825°C for 60 s in a 5% H 2 / 95% N 2 gas ambient was performed to reduce the density of defects in the crystal created during the low-temperature growth. 28,29 Devices with a circular mesa structure and two bonding pads were fabricated using photolithography and wet etching ͓Fig. 1͑b͔͒.…”

High 5.2 peak-to-valley current ratio in Si/SiGe resonant interband tunnel diodes grown by chemical vapor deposition

“…Maximum PVCR is obtained when these two competing factors are balanced. Since CVD growth is closer to equilibrium than LT-MBE, it is expected to incorporate fewer point defects 23 and, hence, lower valley currents. This is the highest PVCR ever reported for CVD grown Si-based tunnel diodes.…”