Hyeon Deok Yang

Nanoscale dry etching of germanium by using inductively coupled CF4 plasma

The nanoscale dry etching of germanium was investigated by using inductively coupled CF4 plasma and electron-beam lithography. The optimal dose of PMMA as E-beam lithography resist was ∼200 mC/cm2. When ICP Power was 200W, CF4 gas flow rate was 40 sccm, and process pressure was 20 mTorr, it had a smooth surface and good etch rate. The etching selectivity of Ge wafer to PMMA resist was as low as ∼1.5. Various sub-100 nm dry-etching patterns have been obtained. SEM pictures showed good profile qualities with a smooth etching sidewall and ultrasmall etching features.

Growth and characterization of Si1−xGetx QDs on Si/Si0.8Ge0.2 layer

Si1−xGetx QDs structures were grown onto Si/Si0.8Ge0.2 layer using RPCVD system. Ge composition in Si1−xGetx QDs was determined as about 30% and 40%. Three peaks are observed in Raman spectrum, which are located at about 520, 410, and 295 cm−1, corresponding to the vibration of Si-Si, Si-Ge, and Ge-Ge phonons, respectively, and the Si1−xGetx QDs related peak was located at 490 cm−1. The PL spectrum that originates from the radiative recombinations came from the Si substrate, the Si0.8Ge0.2 layer and Si1−xGetx QDs. For Si1−xGetx QDs, the transition peaks related to the QDs region observed in the photocurrent spectrum were preliminarily assigned to electron-heavy hole (e-hh) and electron-light hole (e-lh) fundamental excitonic transitions.