ArcAdiA

Ultradense phosphorus in germanium delta-doped layers

2009-03-31T22:00:00Z

Ultradense phosphorus in germanium delta-doped layers Scappucci, Giordano; Capellini, Giovanni; Lee, W. C. T.; Simmons, M. Y. 2009-04 Applied Physics Letters 94 162106 Phosphorus (P) in germanium (Ge) delta-doped layers are fabricated inultrahigh vacuum by adsorption of phosphine molecules onto anatomically flat clean Ge(001) surface followed by thermal incorporationof P into the lattice and epitaxial Ge overgrowth by molecular beamepitaxy. Structural and electrical characterizations show that P atomsare confined, with minimal diffusion, into an ultranarrow 2-nm-widelayer with an electrically active sheet carrier concentration of4x10(13) cm(-2) at 4.2 K. These results open up the possibility ofultranarrow source/drain regions with unprecedented carrier densitiesfor Ge n-channel field effect transistors.

Atomic-scale patterning of hydrogen terminated Ge(001) by scanningtunneling microscopy

2009-11-30T23:00:00Z

Atomic-scale patterning of hydrogen terminated Ge(001) by scanningtunneling microscopy Scappucci, Giordano; Capellini, Giovanni; Lee, W. C. T.; Simmons, M. Y. 2009-12 Nanotechnology 20 495302 In this paper we demonstrate atomic-scale lithography on hydrogenterminated Ge(001). The lithographic patterns were obtained byselectively desorbing hydrogen atoms from a H resist layer adsorbed ona clean, atomically flat Ge(001) surface with a scanning tunnelingmicroscope tip operating in ultra-high vacuum. The influence of thetip-to-sample bias on the lithographic process have been investigated.Lithographic patterns with feature-sizes from 200 to 1.8 nm have beenachieved by varying the tip-to-sample bias. These results open up thepossibility of a scanning-probe lithography approach to the fabricationof future atomic-scale devices in germanium.

Influence of encapsulation temperature on Ge:P delta-doped layers

2009-11-30T23:00:00Z

Influence of encapsulation temperature on Ge:P delta-doped layers Scappucci, Giordano; Capellini, Giovanni; Simmons, M. Y. 2009-12 Physical Review B 80 233202-1 - 233202-4 We present a systematic study of the influence of the encapsulationtemperature on dopant confinement and electrical properties of Ge:Pdelta-doped layers. For increasing growth temperature we observe anenhancement of the electrical properties accompanied by an increasedsegregation of the phosphorous donors, resulting in a slight broadeningof the delta layer. We demonstrate that a step-flow growth achieved atsimilar to 530 degrees C provides the best compromise between highcrystal quality and minimal dopant redistribution, with an electronmobility similar to 128 cm(2)/Vs at a carrier density 1.3x10(14)cm(-2), and a 4.2 K phase coherence length of similar to 180 nm.