V. Kossov

High-dose Al-implanted 4H-SiC p+-n-n+ junctions

p+-n-n+ junctions were fabricated by ion implantation with Al of low-doped epitaxial n layers of 4H-SiC grown by chemical vapor deposition on commercial 4H-SiC wafers both with and without reduction of micropipe densities. It was shown that, using high levels of Al ion doping (5×1016u200acm−2) in combination with rapid thermal anneal, single-crystal p+-4H-SiC layers can be obtained. These layers do not form barriers at the contact metal–semiconductor interface and do not introduce additional resistance into structures with p+-n junctions. This significantly reduces the forward voltage drop across the structure in a wide range of current densities up to 104u200aAu200acm−2.

Gettering Effect with Al Implanted into 4H-SiC CVD Epitaxial Layers

Structural peculiarities of thin Al high dose ion implanted layers in 4H-SiC CVD epitaxial layers after short high-temperature pulse annealing w ere studied using secondary ion massspectroscopy (SIMS) and transmission electron spectroscopy (TEM). E lectrical properties of the Alimplanted layers were investigated by Hall effect measureme nts up to 1000 K. The improvement of the structural perfection of 4H-SiC CVD epitaxial layers near p-interface after Al ion implanted pn junction formation, revealed earlier, was confirmed by deep level tr ansient spectroscopy (DLTS) investigations in the temperature range 80-600 K. The possibili ty of an ion gettering effect in 4H-SiC CVD epitaxial layers after high dose Al i mplantation and high-temperature pulse annealing is discussed. Introduction 4H-SiC is the most promising SiC polytype for manufacturing high-powe r, high-voltage and high-speed electronic devices with stable operation in extreme envir onments. High dose Al implantation with a short high temperature thermal anneal has rece ntly b en shown to ensure the creation of narrow p -layers which can be used as effective hole injection regions in S iC devices [1]. At the same time it has been shown that after Al ion implant ation doped (ID) p n junction formation, the improvement of the structural perfection of 4H-SiC CVD epitaxial layers at the depth of about 4 μm was accomplished [2]. The reduction, or absence of, Al 2O3 inclusions and other defects in the CVD epitaxial layers close to the p n junction, provided for the absence of recombination centers in this area which, in its turn, led to the incr ase of the diffusion lengths of the minority carriers –holes(L p) by a factor of more than 2 compared to the virgin CVD epitaxial layers. This fact contributed to a partial modulation of the n-base r egion by injected holes and lowered the differential resistance values in the diodes to less than 3×10 Ωcm [3]. However, it is well known that gettering effects exist for ion implantation in ot her semiconductors [4-6]. We suggest that a similar gettering effect of implanted ions into 4H-S iC could explain the data obtained. This paper presents results on the investigation of the gettering e ffect of Al implanted into 4H-SiC CVD epitaxial layers annealed by short high-temperature pulses.

Material quality improvements for high voltage 4H-SiC diodes

Abstract The influence of thin 4H-SiC buffer layers grown by liquid phase epitaxy (LPE) on structural quality of 4H-SiC low-doped epitaxial layers, grown by chemical vapor deposition (CVD) was investigated in detail. A dramatic defect density reduction in CVD epitaxial layers grown on commercial wafers with buffer LPE layer was detected. P + n junctions were formed on these CVD layers by high dose Al ion implantation followed by rapid thermal anneal. It was shown that both the increase of diffusion lengths of minority carriers (Lp) in CVD layers and the forming of p + -layers after Al ion implantation and high temperature anneal lead to superior device characteristics.

Influence of ion implantation on the quality of 4H-SiC CVD epitaxial layers

The effect of ion implantation doping (ID) with high doses of Al followed by short high-temperature annealing of n-type 4H-SiC epitaxial layers grown by chemical vapor deposition (CVD) has been stu ...

4H-SiC High Temperature Spectrometers

The detector structures based on Al ion-implanted p+-n junctions in 4H-SiC have been manufactured and tested at temperatures up to 170oC by α-particles with energies of 3.9 and 5.5 MeV. Structural peculiarities of thin Al high dose ion implanted layers before and after short high temperature activation annealing were studied by combination of Rutherford back scattering/channeling spectrometry and cross-sectional transmission electron microscopy. The detector structures fabricated on this thin ion implanted p+-n junctions operated in the temperature range of 16-170 oC with reproducible stable spectrometric characteristics. The charge collection efficiency and the energy resolution of detectors improved with rising temperature up to 170 oC, that was obtained in SiC detectors for the first time.

Spectrometric properties of SiC detectors based on ion-implanted p+-n junctions

Results of spectrometric studies of nuclear radiation detectors based on p+-n junctions formed in 4H-SiC films are presented for the first time. The junctions were fabricated by ion implantation of aluminum into 26-μm-thick CVD-grown epitaxial 4H-SiC layers with an uncompensated donor concentration of (3–5) × 1015 cm−3. The detector characteristics were measured in testing with natural-decay alpha particles with energies of 3.35 and 5.4 MeV. The collection efficiency of charge generated by 3.35 MeV alpha particles was as high as 100% at an energy resolution of ≲ 2%.

Silicon carbide detectors of high-energy particles

The results of studying 4H-SiC p+-n junctions ion-implanted with aluminum as detectors of high-energy particles are reported. The junctions were formed in SiC epitaxial films grown by chemical vapor deposition. The concentration of uncompensated donors was (3–5)×1015 cm−3, and the charge-carrier diffusion length was Lp=2.5 µm. The detectors were irradiated with 4.8–5.5-MeV alpha particles at 20°C. The efficiency of collection of the induced charge was as high as 0.35. The possibilities of operating SiC detectors at elevated temperatures (∼500°C) are analyzed.

Photoelectric properties of p+-n junctions based on 4H-SiC ion-implanted with aluminum

The photoelectric properties of p+-n junctions that were based on 4H-SiC ion-implanted with aluminum and were formed in lightly doped n-type epitaxial layers grown by chemical vapor deposition were studied. It is shown that such photodetectors combine in full measure the advantages of photostructures formed on the basis of Schottky barriers and epitaxial p-n junctions. The results of the theoretical calculation of spectral characteristics of ion-implanted photodetectors are in good agreement with experimental data. The structures feature an efficiency of collection of nonequilibrium charge carriers close to 100% in the spectral range of the photon energies of 3.5–4.25 eV.

Determination of nitrogen in silicon carbide by secondary ion mass spectrometry

The emission of atomic and complex nitrogen ions, which are the main impurity determining the n type conduction of silicon carbide, is investigated. It is shown that, among all the secondary ions of the CxN and SixN kind (x = 0, 1, 2, 3), the 26(CN)– fragment exhibits the highest ion yield. The use of an ion peak with a specified mass as an analytical signal provides a detection limit for nitrogen in SiC at a level of 1016 cm–3. This result is attained in measurements at high mass resolution (M/ΔM = 7500, interference peak 26(13C2)–).