The structure and properties of metal-semiconductor interfaces

High barrier Yb/p‐InP metal‐insulator‐semiconductor (MIS) and metal‐semiconductor (MS) junctions were fabricated by evaporation of Yb on InP:Zn substrates. The capacitance‐voltage (C‐V) and current‐voltage (I‐V) characteristics of these devices were measured over a wide range of temperatures. From the room‐temperature forward I‐V data, the values of 1.06 and 1.30 for the ideality factor (n) were obtained for the MIS and MS diodes, respectively. The higher value of n was attributed to an order of magnitude higher density of interface states in the MS junction than in the MIS diodes. The I‐V/T data over the temperature range 190–400 K, indicated that the forward current transport in the Yb/p‐InP MIS junction was controlled by the thermionic‐field emission (TFE) mechanism. The analysis of the reverse saturation current I0 in terms of the TFE model provided a value of 1.07±0.03 V for the zero bias, zero temperature barrier height (φ0) which was in close agreement with the value of φ0=1.03±0.04 V, provided by ...

Temperature dependence of the electrical characteristics of Yb/p-InP tunnel metal-insulator-semiconductor junctions

The current-voltage (I-V) and capacitance-voltage (C-V) characteristics of GaAs metal-insulator-semiconductor (MIS) Schottky barrier diodes are investigated over a wide temperature range and compared with MS diodes. The effects of the insulating layer on barrier height and carrier transport are delineated by an activation energy analysis. Excess currents observed at low forward and reverse bias have also been analyzed and their cause identified. A capacitance anomaly consistently noticed in MIS Schottky barriers is resolved by stipulating a non-uniform interfacial layer, and a self-consistent model of the GaAs MIS Schottky barrier is developed by analyzing I-V and C-V data of both MIS and MS diodes.

Electrical characteristics of GaAs MIS Schottky diodes

A method to fabricate Au- n -type InP Schottky contacts with an interfacial layer has been developed. The interfacial layer is formed by deposition of a P x O y layer and reaction of this layer with the InP substrate. The current-voltage and capacitance-voltage characteristics are measured at various temperatures. Excellent rectification is found in the fabricated contacts. The observed reverse currents are very low. The ideality factors are around 1.15. Apparent barrier heights qφ B are evaluated from the extrapolated forward saturation current I s . They are found to be sufficiently high. The typical value of qφ B at room temperature is obtained as 0.88 eV. The Richardson plot ln( I s / T 2 ) vs 1/ T is well fitted in a straight line, where T is the temperature. From the Richardson plot, the true barrier height is estimated to be 0.41 eV. The effects of the interfacial layer are also discussed.

A new method to fabricate Au/n-type InP Schottky contacts with an interfacial layer

Unintentionally doped (100) InP wafers were ‘‘cleaned’’ with 12 different etching procedures, either found in the current literature or adapted from Si technology. We present the results of x‐ray photoelectron spectroscopy (XPS) and Rutherford backscattering experiments together with electrical properties of Au/InP contacts realized on the same samples. We can distinguish: first, the solutions which result in a rather clean InP surface and give metal‐semiconductor Au/InP diodes from those which lead to an approximately 20‐A‐thick oxide layer and give metal‐insulating‐semiconductor structures, and second, the solutions which give electrically stable structures from those which lead to very unstable ones. Detailed electrical measurements [J‐V; J(V,T); C(V,T)] have been performed on two kind of stable surfaces: on ‘‘clean’’ etched ones and on one oxidized with NH4OH‐H2O2‐H2O (5:1:100) solution. For the first ones, a quasi‐ideal metal‐semiconductor diode is found. For the oxidized surfaces, current flow is controlled by pure tunneling through the oxide layer. A correlation between surface composition evaluated with XPS and surface electrical properties has been clearly established: the electrical properties of the relatively P‐rich oxides are quite unstable while the others, In rich, remain stable over several months. The composition and the nature of the various oxides are discussed.

Chemical cleaning of InP surfaces: Oxide composition and electrical properties

Metal-semiconductor surface barriers have been formed by the vacuum evaporation of Au/Ti on to epitaxially grown films of n-type InP. The current and capacitance of these devices were measured as a function of voltage at several temperatures and analysed in terms of existing theories. The particular contact fabrication process which has been used produces a relatively high (0.53 eV) room-temperature barrier height; the temperature dependence of the barrier height (4.8*10-4 eV K-1) is approximately equal to that of the energy gap in InP. The diodes exhibited ideality factors of approximately 1.07 and room-temperature saturation current densities approximately 3*10-5 A cm-2.

K P Pande

Papers

Electrical characteristics of Au/Ti-(n-type) InP Schottky diodes