| AVS 60th International Symposium and Exhibition | |
| Surface Science | Wednesday Sessions |
| Session SS+EM-WeA |
| Session: | Semiconductor Surfaces and Interfaces |
| Presenter: | T. Kent, University of California San Diego |
| Authors: | T. Kent, University of California San Diego M. Edmonds, University of California San Diego E. Chagarov, University of California San Diego R. Droopad, Texas State University A.C. Kummel, University of California San Diego |
| Correspondent: | Click to Email |
III-V semiconductors are expected to be used as the channel material in future metal oxide semiconductor field effect transistors (MOSFETs) due to their intrinsically higher electron mobilities. Previous work has shown that the InGaAs (2x4) surface reconstruction has promising CV characteristics and is a viable choice for use as the channel[1], but there is a fundamental problem with this surface. Edmonds et al. showed that all In/GaAs (2x4) surfaces contain at least 8% α2-(2x4) unit cells and when alloying In/Ga to form InGaAs that number jumps to a minimum of 48%.[2] The α2-(2x4) unit cell is missing one As-As dimer on the row which results in metallic In-Ga bonds. These metallic bonds cause bond angle strain in the edge As atoms which prefer to be in tetrahedral sp3 bonding configuration. This strain causes a conduction band edge state in the (2x4) density of states (DOS), and prevents the Fermi level from being efficiently modulated without proper passivation techniques. In order to improve III-V based MOSFET performance it is crucial to passivate the intrinsic α2-(2x4) defect unit cells. Trimethylaluminum (TMA) does not react with the defect unit cells; therefore, in order to achieve an ideal interface a dual passivation scheme is necessary. In this study density functional theory (DFT) was used to show that there is a conduction band (CB) edge state associated with the defect unit cells. By inserting –OH, -SH, or –NH2 into the metallic In-Ga bonds and to the edge In/Ga dangling bonds after TMA passivation, it is possible to fully passivate the CB edge state. Scanning tunneling microscopy and spectroscopy (STM/STS) was utilized to show that it is possible selectively passivate the α2-(2x4) by dosing H2O (g) and maintain an unpinned Fermi level. Subsequently TMA was dosed to passivate the β2-(2x4) unit cells, STM shows an atomically ordered surface exists and ALD of Al2O3 was nucleated in each unit cell. STS showed that by using this dual passivation technique the Fermi level remained unpinned. Using the optimized oxidant dosing temperatures, the McIntyre group at Stanford has shown this dual passivation technique results in superior CV characteristics in MOSCAPs consistent with the dual passivation technique improving InGaAs based MOSFETs.
1)Hwang, Y,et al., Influence of trimethylaluminum on the growth and properties of HfO[sub 2]/In[sub 0.53]Ga[sub 0.47]As interfaces. Applied Physics Letters, 2011. 98(5): p. 052911.
2)M. Edmonds, W.M., T. Kent, E. Chagarov, A. C. Kummel, ECS Transactions, 2012. 50(4): p. 129-140.