Modulation doping in GexSi1−x/Si strained layer heterostructures

Abstract

We report the first observation of the modulation doping effect in Si/Ge0.2Si0.8 heterojunctions grown by molecular beam epitaxy. Peak hole mobilities of ∼3300 cm2 V−1 s−1 have been observed at 4.2 K. These values, although nonoptimum, are comparable to the best reported values for holes in Si/SiO2 inversion layers. Low temperature, angular dependent, Shubnikov–de Haas measurements have demonstrated the two-dimensional nature of the hole gas and yield a surface carrier density of 3.5×1011 cm−2. From the temperature dependence of the Shubnikov–de Haas amplitudes a hole effective mass of 0.30±0.02mo has been derived. Identical measurements on n-type heterojunctions having the same Ge content (x=0.2) have failed to show a sustained enhancement of mobility at low temperatures, indicating that ΔEv≫ΔEc.

Bending induced electrical response variations in ultra-thin flexible chips and device modeling

“…For example, substrate-induced (global) or processinduced (local) uniaxial straining of Si, Ge-, and III-V (e.g., GaAs) alters the band structure so as to enhance the performance of metal-oxide-semiconductor field-effect-transistors (MOSFETs). [14][15][16][17][18][19][20][21][22] A few review articles have covered aspects such as uniaxial and biaxial strain on carrier mobility in MOSFETs, [23][24][25][26] with a theoretical analysis of the physics of strained MOSFETs for different wafer surface orientations, channel directions, gate electric fields, and materials. 23,24,26 These studies have positive implications for similar investigations in bendable or flexible electronics.…”

Modulation doping of transition metal dichalcogenide/oxide heterostructures

“…Modulation doping has been widely used in III-V compound heterojunction superlattices to eliminate the influence of ionized impurity scattering. [14][15][16] In the heterojunction device, the ionized dopants and electrons are confined to two different adjacent layers. As a result, both the mobility and carrier concentration are well maintained.…”

Epitaxial growth of two-dimensional electron gas (2DEG) in strained silicon for research on ultra-low energy electronic processes

“…Corresponding advancement in the quality of 2-D electron systems in Si has been lagging behind as far as their quality at cryogenic temperatures is concerned, in spite of the very mature Si MOSFET technology. In 1984, People et al first observed the two-dimensional hole gas (2DHG) in modulation-doped Si 0.8 Ge 0.2 films grown on Si (001) substrates [4]. In the following year, Abstreiter et al studied strained silicon grown on partially relaxed Si 1 − x Ge x substrate with type-II band alignment and observed the presence of two-dimensional electron gas in Si [5].…”