Density of states of a two-dimensional electron gas at semiconductor surfaces

Abstract

The formation of a two-dimensional ͑2D͒ electron channel at semiconductor surfaces has been studied by high-luminosity and high energy-resolution ultraviolet photoelectron spectroscopy. A large variety of bandbending sources ͑alkali metals, silver and antimony adatoms, cleavage defects͒ on different narrow-gap III-V͑110͒ substrates ͑InAs, InSb͒ has been used. The measured photoemission spectral density in the semiconductor conduction band shows a steplike structure, consistent with the description of a jelliumlike 2D electron gas confined in a potential well, and it is independent of the band-bending sources. A self-consistent solution of the Poisson and Schrödinger equations gives the energy eigenvalues, the eigenstates, and the spectral density, in excellent agreement with the collection of photoemission results. Moreover, the accumulated charge density ranges between 3ϫ10 11 and 2ϫ10 12 electrons/cm 2 , consistent with previous experimental results on plasmon excitations.

Effect of a skin-deep surface zone on the formation of a two-dimensional electron gas at a semiconductor surface

“…We focus on InAs, as it is probably the best studied material showing native accumulation layers [1][2][3]9,10,[30][31][32], having as well a large technical application potential [33][34][35]. The band bending at InAs surface depends on its orientation and reconstruction as well as on adsorbates [2,9,10,30,32,[36][37][38][39][40].…”

“…The band bending at InAs surface depends on its orientation and reconstruction as well as on adsorbates [2,9,10,30,32,[36][37][38][39][40]. We use sulfur treatment on the (001) surface in order to control the bending [41].…”

“…Two-dimensional electron gases (2DEGs) occurring at surfaces of semiconductors have been studied for many years due to their rich phenomenology and extreme technological relevance [1][2][3][4][5][6][7][8][9][10][11][12][13]. The 2DEGs arise following subsurface confinement of conduction electrons caused by an electric field.…”

Hydrogen on III-V (110) surfaces: Charge accumulation and STM signatures

“…[14][15][16][17] Weber et al 13 recently showed that in most cases this can be accounted for by the presence of In adatoms on the surface, but for freshly cleaved (110) surfaces no such defect should occur, since cleaving only encourages the growth of vacancies, 18 formed by Langmuir evaporation. 19 They examined the surface states, and showed that they cannot be used to explain charge accumulation either.…”

Accurate evaluation of subband structure in a carrier accumulation layer at an n-type InAs surface: LDF calculation combined with high-resolution photoelectron spectroscopy

“…A minute amount of adsorbate, such as H, 1 N, 2 Sb, 3,4 Ag, 4, 5 K, 4 Cs, 4,6 Fe, 7 and Nb 8 atoms, or a tiny quantity of surface defects 9 induces a carrier-accumulation layer at an n-type InAs(110) surface. Increasing adsorption gives rise to a gradual formation of a carrier-accumulation layer at the surface.…”