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Electronic Transport through Silicon (a‐Si:H) Barriers in Hydrogenated Amorphous Germanium (a‐Ge:H)
Author(s) -
Drüsedau Thilo P.
Publication year - 1995
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2221870111
Subject(s) - ohmic contact , germanium , materials science , heterojunction , electrical resistivity and conductivity , conduction band , conductivity , amorphous solid , activation energy , condensed matter physics , silicon , semiconductor , silane , thermal conduction , electron , optoelectronics , chemistry , nanotechnology , crystallography , electrical engineering , physics , engineering , layer (electronics) , quantum mechanics , composite material
Films of a‐Ge:H containing single and double barriers of a‐Si:H with a total thickness of 10 nm are prepared by rf PCVD from germane and silane, respectively. The current–voltage characteristics of the sandwich structures are smooth and do not show any irregularities. The differential conductivity σ( E ) of the structures is nearly step‐like with values of 3 × 10 −8 and 10 −5 ω −1 cm −1 for external fields below 200 and above 1000 V/cm, respectively. The ohmic conductivity (at lower fields) of the ultrathin a‐Si:H barriers is identical to bulk a‐Si:H and is 10 −10 Ω −1 cm −1 . This implies a discontinuity of the conduction band edge at the a‐Si:H/a‐Ge:H interface of 0.3 eV. For low fields and below 240 K, there is ohmic hopping with an activation energy of 0.3 eV. The internal field in the barrier reaches very large values of 4 × 10 5 V/cm. For the first time, the observation of a vanishing and a negative differential resistivity of the a‐Si:H barriers even at room temperature is reported. It is concluded that there is no real quantum confinement in heterostructures based on amorphous semiconductors.