T. Kociniewski

Determination of the phosphorus content in diamond using cathodoluminescence spectroscopy

In n-type diamond doped with phosphorus, exciton properties have been investigated by cathodoluminescence as a function of the phosphorus concentration and the temperature. The homoepitaxial diamond layers were grown by microwave plasma-assisted chemical vapor deposition and doped using a liquid organic precursor of phosphorus (tertiarybutylphosphine). The phosphorus concentration ranges from 5.2×1016 to 3.3×1018 cm−3 as measured by secondary ion mass spectrometry. It is shown that the ratio between the luminescence intensities of the neutral phosphorus-bound exciton and the free exciton follows the dopant concentration. Calibration graphs are presented to determine the phosphorus contents in diamond using cathodoluminescence spectroscopy.

Conversion of p-type to n-type diamond by exposure to a deuterium plasma

The lack of a shallow donor in diamond with reasonable room temperature conductivity has been a major obstacle, until now, for the realization of many diamond based electronic devices. Most recently it has been shown that exposure of p-type (B doped) homoepitaxial diamond layers to a deuterium plasma can result in the formation of n-type diamond with a shallow donor state (Ea=0.34eV) and high room temperature mobility (430cm2∕Vs) [Z. Teukam et al., Nat. Mater. 2, 482 (2003); C. Saguy et al., Diamond Relat. Mater. 13, 700 (2004)]. Experimental results, based on the comparison of secondary ion mass spectrometry profiles of B and D and Hall effect measurements at different temperatures are presented. They confirm the previous speculation that some deuterium related complex is responsible for the donor activity in diamond. These donors are shown to be formed in a two-step process. First, deuterium diffuses into the entire B containing layer rather slowly, being trapped by the boron acceptors and passivating t...

Impurity-to-band activation energy in phosphorus doped diamond

The value of the impurity-to-band activation energy EA of a dopant is a basic feature of the electrical conductivity of semiconductors. Various techniques were used to determine EA in n-type diamond doped with phosphorus, giving values of EA varying from 0.43 eV to 0.63 eV, the value EA of 0.6 eV being commonly accepted for the ionization energy of phosphorus donors in diamond. Nevertheless, up to now, the dispersion of the experimental values of EA remains unexplained. In this work, we investigate the electrical properties of a set of n-type diamond homoepitaxial films with different phosphorus concentrations by Hall effect measurements in order to deduce EA and to understand the evolution of this energy with the dopant concentration. We show that, below 2 × 1019 cm−3 phosphorus, the decrease of EA is mainly controlled by the concentration of ionized defects resulting from the donor compensation. The role of ionized defects in the decrease of EA is analyzed on the basis of existing models adapted to the case of diamond. The proposed model provides a correct description of the experimental data. It can be used to quantitatively predict the activation energy of phosphorus in n-type diamond for given donor and compensating acceptor concentrations.

New Investigation Possibilities on Forward Biased Power Devices Using Cross Sections

For the first time, it is demonstrated in this letter that high-power silicon devices [diodes and insulated gate bipolar transistor (IGBTs)] can be forward biased and remains functional after cross sections. Sample preparation is presented, and electrical characterizations of a high-power diode and IGBT (600 V-200 A) have been performed in steady on-state. Infrared thermography on the cross-section surface using a macro-lens with high spatial resolution has allowed characterizing the vertical thermal distribution inside the power diode during forward bias. The impact of this work is that it opens a wide field of investigation in high-power semiconductor device characterization under forward bias.

Temperature mapping by μ-Raman spectroscopy over cross-section area of power diode in forward biased conditions

Abstract It has been demonstrated that high power devices like power diodes and IGBTs (Insulated Gate Bipolar Transistors) could remain functional after cross section. This has opened a field of possibilities for the characterization of distribution of physical quantities over vertical cross-sections of power semiconductor devices. In this paper, we used the Raman spectroscopy technique to perform the mapping of temperature distribution over the cross section area of a forward biased power PIN diode. As the mechanical stresses lead to shift the Raman peak, for accurate measurements in strained structures, it is necessary to deconvolute the influence of stress and temperature on Raman shift to measure temperature. Another solution consists in measuring the Full Width at Half Maximum (FWHM) of the silicon related Raman peak. This parameter depends only on the temperature and the crystalline quality of material. By this way, it is possible to measure the temperature accurately without any artifact due to the stress. Using this method, we have measured the temperature distribution over a vertical cross section of a power diode in forward bias conditions and strained by its packaging. The residual stress in the chip cross section was also estimated at room temperature in order to validate the FWHM choice for temperature calibration.

Distributed electro-thermal model of IGBT chip – Application to top-metal ageing effects in short circuit conditions

Abstract A new distributed electro-thermal model has been developed in order to analyze electrical and thermal mappings of power devices during critical operations. The model is based on dividing power device into a vertical multilayer structure, with each layer discretized into multiple slab volumes. This model has been used to evaluate the effects of chip metallization ageing on temperature distributions and current sharing between cells within an IGBT chip during short-circuits operations. Dynamic latch-up failures during short-circuit operations has been investigated.

Mechanical and thermal stresses characterization maps on cross-sections of forward biased electronic power devices

Characterization of mechanical and thermal stresses inside the power devices crystal is required for physics of failure analyses of power electronic devices. Recent results have shown the capability to keep this power device functional after cross section. The use of Raman spectroscopy to map mechanical stress and temperature distributions on cross-sections of IGBT (Insulated Gate Bipolar Transistor) devices in forward bias conditions is reported. Mechanical and thermal stresses maps were made in unbiased and forward biased using μ-Raman technique with spatial resolution up to 500nm. Temperature and stress contributions on Raman diffusion were deconvoluted fitting Full Width at Half Maximum (FWHM) and position of the Stokes peak. For the first time, it was possible to quantify experimentally mechanical stress and temperature evolution during operation. These results give experimental data on thermo-mechanical coupling in power devices and are compared with numerical models made with finite elements under ANSYS with a focus on IGBT elementary cell areas.

Some Recent Advances on the n-Type Doping of Diamond

The n-type doping of diamond with phosphorus suffers from defects reducing the electron mobilities and inducing some degree of compensation. In addition, the relatively high ionization energy (0.6 eV) of phosphorus severely limits the electrical activity of the dopants. Here, we present two recent advances of the n-type doping of diamond. One is based on the significant reduction of the compensation ratio of highly compensated phosphorus-doped diamond by thermal annealings. The second one presents the possibility of converting p-type boron-doped diamond into n-type by deuterium diffusion and formation of deuterium-related shallow donors with ionization energy of 0.33 eV.