Growth and characteristics of Fe-doped GaN

Universal iron behaviour in Zn-, Cd- and Be-doped p-type InP

A reproducible technique for preparing semi-insulating (SI) InP by high temperature annealing can only be achieved by controlled doping with Fe in a sufficient concentration for compensation. However, a successful and reproducible method to adjust the low Fe content has not been developed up to now. In this paper, we report two different experimental approaches to control the Fe content by using either precompensated starting material or an Fe source for doping via the vapor phase. InP wafers (2′ diam) which were lightly predoped with Fe ([Fe] < 5 × 1015 cm−3) during liquid encapsulated Czochralski (LEC) growth were converted from the semiconducting to the SI state and were subsequently analyzed by laterally resolved resistivity measurements. These wafers show high resistivity uniformity (p ≈1 × 108 Ω-cm) which has never previously been achieved with LEC material at such a low Fe concentration. Furthermore, we present the first results of annealing nominally undoped InP with a defined Fe source.

Control of low Fe content in the preparation of semi-insulating InP by wafer annealing

The authors attempted to grow a semi-insulating silicon carbide (SiC) epitaxial layer by in situ iron doping. The homoepitaxial growth of the iron-doped 4H-SiC layer was performed by metal-organic chemical vapor deposition using the organo-silicon precursor bis(trimethylsilylmethane) (C7H20Si2) and the metal-organic precursor t-butylferrocene (C14H17Fe). For the measurement of the resistivity of the iron-doped 4H-SiC epilayers, the authors used the on resistance of Schottky barrier diode. Based on the measurement of the on resistance, it is shown that the free carrier concentration was decreased with increasing partial pressure of t-butylferrocene. The resistivity of the iron-doped 4H-SiC epilayer was about 108Ωcm.

Homoepitaxial growth and electrical characterization of iron-doped semi-insulating 4H-SiC epilayer

The optimum conditions for the fabrication of semi‐insulating InP epitaxial layers grown by metalorganic chemical‐vapor deposition are investigated in a comparative study of the structural, electrical, and diffusive properties of Fe‐ and Ti‐doped material. Thermally stable InP:Fe layers with resistivities approaching the intrinsic limit can be prepared in an environment of n‐type material if the Fe concentration does not exceed but is close to its solubility limit of 8×1016 cm−3 at 640 °C. In contact with p‐type layers, however, semi‐insulating characteristics of InP:Fe turn out to be difficult to reproduce because of a pronounced interdiffusion of Fe and p‐type dopants. Here, Ti doping of InP is shown to be a useful scheme for the fabrication of high‐resistivity layers. New processes for the deposition of InP:Ti using (C5H5)2Ti(CO)2 and Ti[N(CH3)2]4 as metalorganic precursors are described in detail. Ti is found to compensate up to 2×1016 cm−3 of shallow acceptors in metalorganic chemical‐vapor‐phase‐deposition‐grown InP. Ti‐doped InP layers containing more electrically active deep Ti donors than net shallow acceptors exhibit semi‐insulating characteristics with a resistivity of 5×106 Ω cm. Codoping of InP:Fe with Ti turns out to be a universal process for the preparation of thermally stable high‐resistivity layers. If the material is appropriately grown, Fe+Ti doping compensates both excess shallow donors and excess shallow acceptors up to concentrations of 8×1016 and 2×1016 cm−3, respectively. In contrast to InP:Fe, resistivities in excess of 107 Ω cm are obtained in contact with both symmetric n‐ and p‐type current injecting contacts. Moreover, codoping of semi‐insulating InP:Fe with Ti is found to suppress the interdiffusion of Fe and p‐type dopants. Therefore, the outdiffusion and accumulation of Fe in other regions of complex device structures can be significantly reduced. The interdiffusion of Fe and p‐type dopants as well as its suppression by additional doping with Ti, finally, is studied in detail, which enables a comprehensive model accounting for this phenomenon to be developed.

A.M. Pougnet

Papers

Growth of InP in chemical beam epitaxy with high purity tertiarybutylphosphine

Iron incorporation in InP layers using a ferrocene source in atmospheric pressure MOVPE

Carbon doping of GaAs for heterojunction bipolar transistors : a comparison between MBE and CBE

Crystal growth and crystallographic data of some Ln2(MoO4)3 type mixed rare earth molybdates