S.K. Krawczyk

Minority carrier lifetime in MOCVD-grown C- and Zn-doped InGaAs

Heavily C-doped p-type InGaAs has been successfully grown by metalorganic chemical vapor deposition using CBr/sub 4/ as a C precursor. A doping concentration as high as 2/spl times/10/sup 19/ cm/sup -3/ has been reached for as-grown (non-annealed) samples. Photoluminescence measurements have been employed to obtain and compare the non-radiative lifetimes in C- and Zn-doped InGaAs. The minority carrier lifetime of as-grown InGaAs:C samples is significantly lower than for as-grown InGaAs:Zn for the same doping concentration. Carrier lifetimes range from 373 ps (p=6.6/spl times/10/sup 16/ cm/sup -3/) to 1.5 ps (p=2.3/spl times/10/sup 19/ cm/sup -3/) in as-grown InGaAs:C, and from 6.8 ns (p=5.0/spl times/10/sup 16/ cm/sup -3/) to 16.8 ps (p=2.1/spl times/10/sup 19/ cm/sup -3/) in InGaAs:Zn, respectively. InGaAs:Zn grown at the same low temperature (450/spl deg/C) as InGaAs:C has a higher minority carrier lifetime. The minority carrier lifetime difference between InGaAs:Zn and InGaAs:C samples is attributed to lower V/III ratio and hydrogen passivation, as well as, lower growth temperatures for the carbon doped InGaAs samples.

New scanning photoluminescence technique for mapping the lifetime and the doping density: application to carbon doped InGaAs/InP layers and heterostructures

Lifetime and doping characterization of selected layers in epitaxial structures as, for example, p-doped layers encountered in the base of Heterojunction Bipolar Transistors (HBTs) is of great importance for the successful development of these devices. Various techniques exist for the evaluation of such characteristics, including time-resolved photoluminescence and Hall measurements. There is, however, lack of a single, fast, non-destructive, quantitative technique that can provide combined lifetime and doping information and that allows, in particular, spatially resolved measurements with high resolution, as well as, wafer-scale mapping evaluation. This paper addresses these issues and demonstrates the feasibility of the proposed approach by successfully applying it to carbon doped InGaAs.

Evaluation of lattice mismatched InGaAs layers and photodiode arrays by scanning photoluminescence

Scanning photoluminescence (SPL) measurements were used to characterize lattice-mismatched InGaAs/InP heterostructures and to study the correlation between the results of the SPL measurements and the electrical characteristics of the completed p-i-n photodiodes made with this material. Mismatch dislocations, isolated dislocations, and short- and long-range nonuniformities were revealed. Correlations between the results obtained by SPL and the reverse current of the fabricated photodiodes were observed. The defect creation in the epitaxial layers is extremely sensitive to small variations of the process conditions.<<ETX>>

New scanning photoluminescence technique for quantitative mapping the surface recombination velocity in InP and related materials

This paper introduces a new approach, based on Room Temperature (RT) Scanning Photoluminescence (SPL) measurements, for non-destructive quantitative mapping of the surface or interface recombination velocity in compound semiconductor structures. The developed technique is validated and applied here to spatially resolved evaluation of the surface recombination velocity of InP substrates and InGaAs(C)/InP heterostructures.

Growth of InGaAs/InP structures by gas source molecular beam epitaxy on SiO2-patterned substrates for optoelectronic applications

Abstract Gas source molecular beam epitaxy has been used to grow InGaAs/InP epitaxial quantum-well structures in selected areas defined by SiO 2 -masked InP substrates, with the goal of obtaining controlled in-plane variations in the band gap of the InGaAs wells. The dependence of the band gap on mask dimensions, growth temperature and arsenic flux has been studied. Photoluminescence spectroscopy performed on waveguide stripes, ranging from 2–50 μm in width, reveals an increasing red-shift of the peak wavelength with decreasing stripe width. Red-shifts as large as 40 meV are reported for the narrowest stripe widths grown with high substrate temperatures and low arsenic fluxes.

Analysis of the uniformity of the localized area epitaxy by spectrally resolved scanning photoluminescence

In this contribution, room temperature spectrally resolved scanning photoluminescence technique with high spatial resolution (1 /spl mu/m) is introduced and applied to control the uniformity of the composition and of the thickness of quantum well (QW) structures obtained by localized area epitaxy. Furthermore, this technique is applied here to study lateral uniformity of QW InGaAs/InP heterostructures grown by localized area gas source molecular beam epitaxy (GSMBE) at various conditions (temperature, arsine flow rate) and as a function of stripe width and spacing.

Expertise, optimisation and control of InP and related technologies by scanning photoluminescence measurements

It is shown how scanning photoluminescence (SPL) measurements can be used to obtain information about, to optimize, and to control InP and related compound semiconductor technologies. It is shown how the PL intensity from an InP substrate varies after successive steps during four different passivation processes, and the information gained thereby is discussed. An example is presented to demonstrate how SPL measurements can be used to optimize the gate recess step in the realization of InP MISFETs. Two possibilities for the routine inline control of successive steps in the processing of compound semiconductor devices using SPL measurements are described: automatic recognition and counting of defects appearing on SPL images (most of which cannot be revealed by optical microscopy) and analysis of statistical parameters describing the SPL data.<<ETX>>

Use of spectrally resolved scanning photoluminescence for optimizing the growth conditions of InAlAs/InP heterostructures

Optimum growth conditions were determined for InAlAs/InP heterostructure materials based on scanning photoluminescence (SPL), structural and electrical characteristics of wafers. The impact of MOCVD growth parameters such as susceptor rotating speed on compositional and thickness uniformity of the layer is also reported using SPL. SPL and complementary thickness measurements showed the correlation between compositional and thickness uniformity and suggest that the spatial uniformity of the boundary layer is responsible for the spatial uniformity of the grown layers. Thus, the use of non-destructive techniques such as SPL is very useful for optimizing growth parameters. Compositional uniformity as determined by SPL could, for example, be a measure for speed, temperature and boundary layer optimization. Our results show that for the MOCVD reactor geometry and growth conditions used, a low rotating speed of 100 rpm appears to be the optimum for better composition and thickness spatial uniformity.

Demonstration of short range non-uniformities of the spectral parameters of photoluminescence bands in lattice mismatched InAlAs/InGaAs/InAlAs/InP heterostructures

A wide range of InAlAs/InGaAs/InAlAs/InP and InGaAs/InP lattice mismatched heterostructures with different thicknesses and compositions of the InGaAs layer were grown on InP (001) by Molecular Beam Epitaxy (MBE) and investigated with high spatial resolution spectrally resolved scanning photoluminescence. The objective of this contribution is to demonstrate that different types of extended defects (misfit dislocations, threading dislocations, oval-shaped defects) and structural micro-heterogeneity in the InGaAs layers induce significant short range changes of the spectral parameters of the photoluminescence bands.<<ETX>>

Electrical characterization of lattice-mismatched In/sub x/Ga/sub 1-x/As photodiode arrays for detection to 1.7 mu m

Lattice mismatched In/sub x/Ga/sub 1-x/As photodiode arrays used for the detection of up to 1.7 mu m in space applications are discussed. The abnormally high reverse current observed on some diodes is interpreted by the electric field assisted generation process. The role of misfit dislocations in the process seems to be important, as established by the correlation between local lowering of photoluminescence signal and the high reverse current. The detection of one deep level on these photodiodes by admittance spectroscopy measurements is described.<<ETX>>