Surface Properties of Germanium

Abstract

The contact potential (c.p.) and the change of contact potential with illumination (Δc.p.)L, of several germanium surfaces have been measured. The reference electrode used was platinum. It was found that the c.p. could be cycled between two extremes about 0.5 volts apart by changing the gaseous ambient. Ozone or peroxide vapors gave the c.p. extreme corresponding to the largest dipole at the Ge surface. Vapors with OH radicals produced the other extreme. There is a one to one correlation between c.p. and (Δc.p.)L. For 12‐ohm cm n‐type Ge (Δc.p.)L was large and positive when the surface dipole was largest, decreased to zero and became slightly negative as the surface dipole decreased to its smallest value. The variation for 12‐ohm cm p‐type Ge was just opposite as regards both sign and dependence on surface dipole. The surface recombination velocity was found to be independent of c.p. For a chemically prepared surface it was 50–70 cm/sec and 180–200 cm/sec for n and p‐type surfaces respectively. A theory is given that explains the results in terms of surface traps, Na per cm2 donor‐type traps near the conduction band and Nb per cm2 acceptor‐type traps near the filled band. A quantitative fit with experiment is obtained with only one free parameter. The results are direct evidence for the existence of a space charge layer at the free surface of a semiconductor.

Surface photovoltage phenomena: theory, experiment, and applications

“…The surface photovoltage (SPV) is de®ned as the illumination-induced change in the surface potential. This effect, observed at Si and Ge surfaces, was ®rst reported in a short note by Brattain in 1947 [1], followed by a detailed account some years later [2].…”

“…In the earliest studies [2,3] it was assumed that the surface states were in equilibrium with the semiconductor bands, i.e., that Fermi±Dirac statistics [Eq. (2.11)] adequately described the surface state population even under non-equilibrium conditions.…”

“…The time necessary to reach the steady state distribution depends on the thermal cross-sections, which vary over many orders of magnitude. Thus, Bardeen and Brattain [2] (and consequently many others) distinguished between`fast states' and`slow states', according to whether the charge in the surface states follows the illumination (at a given modulation frequency or allowed response time) or not, respectively. Though clearly arbitrary, we adopt this division for the present considerations due to its simplicity.…”

“…The Kelvin probe arrangement has been extensively applied to the measurement of illuminationinduced changes in work function starting from the earliest experiments of Bardeen and Brattain [2], and ever since. This has been achieved by Ohmically contacting the back side of the semiconductor sample to a metallic reference electrode.…”

A Study on Hydrogen Reaction Kinetics of Pt/HfO2/SiC Schottky-Diode Hydrogen Sensors

“…The initial work on this type of sensor can be traced back to the work of Brattain andBardeen in 1953 (Brattain et al, 1953). The sensing properties of this sensor are based on reactions between oxide semiconductors and gases in the atmosphere.…”