Deep Level Transient Spectra Research Articles

Observation of a deep level due to In doping in p-type GaAs

We have observed a peak in deep-level transient spectroscopy DLTS spectra due to the presence of In in mph type='1' p-type GaAs samples. Both In-doped and nominally undoped samples of GaAs grown from a Ga-rich melt were examined. We observed an electron trap at Ev+0.095 eV in the In-doped material. Annealing experiments indicated that the trap level may be generated in In-doped material when not present in measurable quantities in as-grown crystals. However, annealing undoped samples under identical conditions failed to produce the level. We conclude that the electron trap is related to the presence of In in the p-type GaAs.

Entropy-driven metastabilities in defects in semiconductors.

Several defects are known to have metastable configurations that can be accessed by charge-state change, optical excitation, or heating followed by rapid cooling. Typically, each configuration is stable over a broad temperature range and can be studied by spectroscopic techniques. In this Letter, we report the observation of a novel metastability: A configuration change occurs spontaneously and abruptly at a critical temperature, giving rise to a discontinuous, deep-level transient spectrum. We propose that this phenomenon is a manifestation of entropy variations in the configurational space.

Broadening in the deep-level transient spectra of defects in GaAs1-xSbxalloys

GaAs1-xSbx is a substitutionally disordered alloy. Defect parameters such as the defect level E0 in this system can acquire a distribution on account of the random potentials exerted by the As and Sb atoms which are randomly distributed on the anion site. This could lead to a broadening of the deep-level transient spectroscopy (DLTS) spectra. The authors adopt a phenomenological approach and study the qualitative and quantitative features of this broadening. They obtain a simple linear relationship between the spectrum broadening and the disorder parameter. They also present a simple and approximate formula for calculating E0 from a single DLTS spectrum.

Capacitance transient studies of a metastable defect in silicon.

Capacitance-transient-spectroscopy measurements were undertaken to study the properties of a previously reported, electron-irradiation-induced defect in silicon. This defect has been attributed to the boron substitutional-vacancy pair. It appears in two metastable configurations and exhibits at least three electrical levels in the deep-level transient capacitance spectrum.

Electrical characterisation of epitaxially overgrown Si in Si<111>/CoSi 2 /Si metal base transistor

Epitaxial Si<111>/CoSi2/Si heterostructures have been grown using molecular beam epitaxy (MBE) apparatus with the overgrown Si layer doped by Sb coevaporation. Electrical characteristics of the top CoSi2/Si epitaxial Schottky barriers are presented. Current/voltage (I/V), capacitance/voltage (C/V) characteristics and deep level transient spectra (DLTS) show that the overgrown Si material is deviceworthy. Furthermore, transconductance measurements between the emitter and collector of the metal base transistor (MBT) indicate that the high Si quality is obtained with a negligible pinhole density in the base. Measurements of the current gain α in the MBT confirm a value of the CoSi2 ballistic mean free path of 90 Å ± 20 Å.

Deep level defect study of molecular beam epitaxially grown silicon films

We report the result of the study on the electrically active deep level defects in Si films grown by molecular beam epitaxy. A deep level defect at Ec−0.58 eV is consistently obtained for samples grown on substrates with purposely contaminated surfaces. The observed defects are all located within 3000–5000 Å of the epilayer-substrate interface with concentrations in or below 1014 cm−3 range. Secondary ion mass spectroscopic study results indicate the correlation between the substrate surface residual carbon concentration and the observed defect concentration. These defects appear to be higher order defects rather than the single level defects, as evidenced by the asymmetry of the deep level transient spectra. For samples grown on the substrates cleaned using an established surface cleaning method, no deep level defects within the detection limit (∼1012 cm−3 in our case) are observed.

Deep level transient capacitance spectroscopy of defects at native oxide-GaAs interfaces of 〈1̄1̄1̄〉 and 〈100〉 orientations

Deep level transient capacitance spectra are presented for anodically oxidised GaAs MOS structures of 〈1̄1̄1̄〉 and 〈100〉 orientations to show that the interfacial region differs depending on the orientation.

Deep level transient capacitance spectroscopy of defects at native oxide-GaAs interfaces of 〈 [formula omitted][formula omitted][formula omitted]〉 and 〈100〉 orientations

Deep level transient capacitance spectra are presented for anodically oxidised GaAs MOS structures of 〈 1 1 1 〉 and 〈100〉 orientations to show that the interfacial region differs depending on the orientation.

Deep level profiles in boron implanted n-Si

The annealing temperature (280–810 C) dependences of the concentration profiles of the majority carriers (electrons), the main deep level at EC−400 mV, and the implanted boron ions are reported in 0.23 Ω cm (3.1×1016 cm−3) phosphorus-doped n-type silicon which was implanted with 5.0×1011 cm−2 of 200 KeV boron ions. A new constant-capacitance voltage transient (CCVT) method and a new many-deep-level CCVT theory are employed to obtain the deep level profiles whose concentrations are comparable to that of the phosphorus dopant impurity. The measured profile of the implanted boron ions, activated at 810 C, agrees with the projected range theory. Seven peaks are observed above 77 K in the deep-level capacitance transient spectra. The major peak at EC−400 mV has a concentration profile that lags behind the boron ion profile and it anneals rapidly between 420 and 430 C. The broadness and the annealing behavior of the majority carrier concentration profiles suggest the presence of at least two high-concentration deep acceptor-like levels below the midgap and at least one of them is a multiple charge state of the EC−400 mV defect level in the upper half-gap.

Study of GaAs–oxide interface by transient capacitance spectroscopy: Discrete energy interface states

Interface states and bulk GaAs energy levels were simultaneously investigated in GaAs MOS structures prepared by anodic oxidation. These two types of energy levels were successfully distinguished by carrying out a comparative analysis of deep level transient capacitance spectra of the MOS structures and MS structures prepared on the same samples of epitaxially grown GaAs (n?1015 cm−3). The identification and study of the interface states and bulk levels was also pursued by investigating the transient capacitance spectra as a function of the filling pulse magnitude. It was found that in the GaAs–anodic oxide interface there are states present with a discrete energy (0.65 eV below the conduction band) rather than with a continuous energy distribution as previously reported. The value of the capture cross section of the interface states was found to be 1014 to 1015 cm2, which is far more realistic than the extremely large values of 10−8 to 10−9 cm2 reported on the basis of conductance measurements.