Junction and device characteristics of gate-last ge p- and n-MOSFETs with ALD-Al2O3 gate dielectric

Chao Ching Cheng*, Chao-Hsin Chien, Guang Li Luo, Ching Lun Lin, Hung Sen Chen, Jun Cheng Liu, Chi Chung Kei, Chien Nan Hsiao, Chun Yen Chang

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


In this paper, we investigated the characteristics of Ge junction diodes and gate-last p- and n-metal-oxide-semiconductor field-effect transistors with the atomic-layer-deposited- Al2O3 gate dielectrics. The magnitudes of the rectifying ratios for the Ge p+-n and n+-p junctions exceeded three and four orders of magnitude (in the voltage range of ±1 V), respectively, with accompanying reverse leakages of ca. 10-2 and 10-4 A · cm-2, respectively. The site of the primary leakage path, at either the surface periphery or junction area, was determined by the following conditions: 1) the thermal budget during dopant activation, and 2) whether forming gas annealing (FGA) was employed or not. In addition, performing FGA at 300 °C boosted the device on-current, decreased the Al2O3/Ge interface states to 8 × 1011cm-2 · eV-1, and improved the reliability of bias temperature instability. The peak mobility and on/off ratio reached as high as 225 cm2 · V-1 · s-1 and 103, respectively, for the p-FET (W/L = 100 μm/ 4 μm), while these values were less than 100 cm2 · V-1 · s-1 and ca. 103, respectively, for the n-FET (W/L = 100 μm/9 μm). The relatively inferior n-FET performance resulted from the larger source/drain contact resistance, higher surface states scattering, and lower substrate-doping concentration.

Original languageEnglish
Pages (from-to)1681-1689
Number of pages9
JournalIEEE Transactions on Electron Devices
Issue number8
StatePublished - 16 Jul 2009


  • AlO
  • Forming gas annealing (FGA)
  • Gate-last metal-oxide-semiconductor field-effect transistor (MOSFET)
  • Germanium
  • High-k gate dielectrics
  • Junction diode


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