{"id":5661,"date":"2012-07-18T22:27:45","date_gmt":"2012-07-18T22:27:45","guid":{"rendered":"https:\/\/mtlsites.mit.edu\/annual_reports\/2012\/?p=5661"},"modified":"2012-07-18T22:27:45","modified_gmt":"2012-07-18T22:27:45","slug":"mos-interfaces-in-the-inasgasb-system","status":"publish","type":"post","link":"https:\/\/mtlsites.mit.edu\/annual_reports\/2012\/mos-interfaces-in-the-inasgasb-system\/","title":{"rendered":"MOS Interfaces in the InAs\/GaSb System"},"content":{"rendered":"

With the rapid downscaling of CMOS technology, III-V materials have gained much attention due to their high electron mobility. In particular, indium-arsenide and gallium-antimonide are becoming more popular due to their matched lattice constant and their complimentary physical properties, such as bandgap and carrier mobility [1<\/a>] <\/sup>; various heterostructure-based high performance field-effect transistors (FET) and tunneling transistors have been proposed [1<\/a>] <\/sup> [2<\/a>] <\/sup>. On the other hand, this material system faces challenges due to the poor oxide\/semiconductor interface, which results in high interface trap concentration (Dit<\/sub><\/em>) and hence Fermi-level pinning [3<\/a>] <\/sup> [4<\/a>] <\/sup>. Therefore, understanding the metal-oxide-semiconductor (MOS) interface in this material system is critical. This study investigates atomic-layer-deposited (ALD) Al2<\/sub>O3<\/sub> on InAs to provide a preliminary understanding of the Al2<\/sub>O3<\/sub>\/InAs interface.<\/p>\n

On an S-doped n-type InAs substrate, 60 cycles of Al\u00ad2<\/sub>O3<\/sub> are deposited at 200\u00b0C and 250\u00b0C after HCl wet chemical cleaning. Then, a Mo\/Pt\/Au (30 nm\/20 nm\/100 nm) gate stack is formed using electron-beam evaporation; the back contact is formed using Ti\/Au. Finally, 30s post-metallization annealing in N2<\/sub> is carried out. Figure 1 shows the normalized capacitance-voltage (C-V) curves of both samples with frequencies varied from 10kHz to 1MHz. The depletion region of the C-V curve is not sharp and deep, as predicted by simulations [5<\/a>] <\/sup>, which is mainly due to the series capacitance corresponding to Dit<\/sub><\/em>. Still, the comparison between the two samples shows that Al\u00ad2<\/sub>O3<\/sub> deposited at 200\u00b0C yields lower Dit<\/sub><\/em> than 250\u00b0C. Figure 2 plots the C-V hysteresis of the two samples at 100kHz, which reflects the oxide mobile charge near the interface. The results show that the hysteresis is moderate for both samples and that the ALD dielectric quality is promising. Quantitative analysis of the Dit<\/sub><\/em> is ongoing.\u00a0 In summary, InAs\/GaSb is a promising heterojunction system, and research is needed to better understand and optimize the dielectric\/semiconductor interface.<\/p>\n\n\t\t