Structural and transport properties in alloyed Ti/Al Ohmic contacts formed on p-type Al-implanted 4H-SiC annealed at high temperature

Frazzetto, Alessia; Giannazzo, Filippo; Nigro, Raffaella Lo; Raineri, V.; Roccaforte, Fabrizio

doi:10.1088/0022-3727/44/25/255302

Cited by 66 publications

(75 citation statements)

References 40 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…On the other hand, part of the unreacted Al diffused toward Based on this result, the reduction of the Schottky barrier height observed with increasing annealing temperature can be associated with the presence of different phases at the interface with the p-GaN, plausibly with a different work function. A similar behavior has also been already observed on Ti/Al-based contacts to p-type silicon carbide [40], [41]. Clearly, the reduction of the Schottky barrier height enhances the tunneling of the holes through the barrier.…”

Section: Resultssupporting

confidence: 80%

Effects of Annealing Treatments on the Properties of Al/Ti/p-GaN Interfaces for Normally OFF p-GaN HEMTs

Greco

Iucolano

Franco

et al. 2016

IEEE Trans. Electron Devices

View full text Add to dashboard Cite

This paper reports on the behavior of Al/Ti/ p-GaN interfaces as gate contacts for p-GaN/AlGaN/GaN normally off high electron mobility transistor (HEMTs), highlighting the impact of the thermal budget on the metal gate on the device characteristics. In fact, while the devices subjected to an annealing at 800°C show a considerable high leakage current, those with nonannealed Al/Ti gate contacts exhibit a normally off behavior, with a pinch-off voltage V po = +1.1 V and an on/off current ratio of 3 × 10 8 . Temperature-dependent electrical measurements on back-to-back Schottky diodes allowed to determine a Schottky barrier height B of 2.08 and 1.60 eV, for the nonannealed and 800°C annealed gate contacts, respectively. Hence, the increase in the leakage current observed upon annealing at 800°C was attributed to the lowering of the Schottky barrier height B of the metal gate. The interfacial structural characterization explained the barrier lowering induced by the annealing. This scenario was discussed through the simulated band diagram of the heterostructures, considering the experimental values of B . These results provide useful information for the device makers to optimize the fabrication flow of normally off HEMTs with p-GaN gate.Index Terms-AlGaN/GaN heterostructures, enhancement mode operation, high electron mobility transistors (HEMTs), p-GaN, Schottky barrier. 0018-9383

show abstract

Section: Resultssupporting

confidence: 80%

Effects of Annealing Treatments on the Properties of Al/Ti/p-GaN Interfaces for Normally OFF p-GaN HEMTs

Greco

Iucolano

Franco

et al. 2016

IEEE Trans. Electron Devices

View full text Add to dashboard Cite

show abstract

“…(14). This results suggests that an appropriate analysis of TLM data can also provide useful information on the electrical activation of Al dopant in 4H-SiC.. [17]. The solid line corresponds to a fit with the empirical expression EA=E0α NA 1/3 with E0=216 meV and α=3×10 -5 meV cm -1 .…”

Section: Resultsmentioning

confidence: 84%

“…On the other hand, the carrier mobility shows a much weaker dependence on the measurement temperature [17]. Hence, it is possible to approximate the temperature dependence of the sheet resistance as:…”

Section: Resultsmentioning

confidence: 99%

Effect of high temperature annealing (T > 1650 °C) on the morphological and electrical properties of p-type implanted 4H-SiC layers

Spera

Corso

Franco

et al. 2019

Materials Science in Semiconductor Processing

View full text Add to dashboard Cite

This work reports on the effect of high temperature annealing on the electrical properties of p-type implanted 4H-SiC. Ion implantations of Aluminium (Al) at different energies (30 -200 keV) were carried out to achieve 300 nm thick acceptor box profiles with a concentration of about 10 20 at/cm 3 . The implanted samples were annealed at high temperatures (1675-1825 °C). Morphological analyses of the annealed samples revealed only a slight increase of the surface roughness RMS up to 1775°C, while this increase becomes more significant at 1825°C (RMS=1.2nm). Room temperature Hall measurements resulted in a hole concentration in the range 0.65-1.34×10 18 /cm 3 and mobility values in the order of 21-27 cm 2 V -1 s -1 . The temperature dependent electrical measurements allowed to estimate an activation energy of the Al-implanted specie of about 110 meV (for the post-implantation annealing at 1675°C) and a fraction of active p-type Al-dopant ranging between 39% and 56%. The results give useful indications for the fabrication of 4H-SiC JBS and MOSFETs.The main dopant species for SiC are Nitrogen (N) and Phosphorous (P) for n-type doping, and Aluminum (Al) for p-type doping. High post-implantation annealing temperatures (> 1500°C) are typically required to bring these species in substitutional positions and achieve their electrical activation [5,6,7]. In particular, selectively doped p-type regions are key parts of both JBS and MOSFETs and the control of their electrical properties has a significant impact on several devices parameters (e.g., Ohmic contacts formation, device on-resistance, threshold voltage and channel mobility, etc.).Hence, understanding the dependence of the properties of p-type implanted layers on the activation annealing temperature is very important for device manufacturers to set the right process for the optimal device characteristics. In this context, although several investigations reported on the properties of Al-implanted 4H-SiC layers [8,9,10], the large variety of experimental conditions and the evolution of the annealing procedures always make this topic open to scientific discussions.Hall-effect measurements are often used to study the electrical properties of p-type 4H-SiC layers, in order to determine key parameters like the holes concentration and mobility [11]. A critical issue of this methodology is the choice of the Hall scattering factor rH for SiC [12,13]. In fact, the difficulty to extract the mobility and the free hole concentration from Hall measurements is related to the correct knowledge of rH. However, many authors often interpret the experimental Hall results on p-type 4H-SiC assuming rH=1, which in turn leads to an overestimation of the doping level in the material [9,14]. Only few works specifically reported experimental calculations of the Hall scattering factor rH for SiC [15,16], whose findings should be considered for a correct analysis of the currently available data.This paper reports on the morphological and electrical properties of p-type implanted 4H-SiC annealed...

show abstract

“…11,12 In contrast, extracted values of U b vary significantly even if our highest and lowest SBH can be compared to those reported in the literature. 17,18 As a consequence, the variation of the SCR is mainly related to a fluctuation of the SBH. Since the SBH is related to the intimate metal/4H-SiC interface, something is happening either during the VLS growth or contact annealing which favors or not the lowering of the SBH.…”

Section: -mentioning

confidence: 99%

Very low specific contact resistance measurements made on a highly p-type doped 4H-SiC layer selectively grown by vapor-liquid-solid transport

Thierry-Jebali

Vo-Ha

Carole

et al. 2013

Applied Physics Letters

View full text Add to dashboard Cite

This work reports on the performances of ohmic contacts fabricated on highly p-type doped 4H-SiC epitaxial layer selectively grown by vapor-liquid-solid transport. Due to the very high doping level obtained, the contacts have an ohmic behavior even without any annealing process. Upon variation of annealing temperatures, it was shown that both 500 and 800 °C annealing temperature lead to a minimum value of the Specific Contact Resistance (SCR) down to 1.3×10−6 Ω⋅cm2. However, a large variation of the minimum SCR values has been observed (up to 4×10−4 Ω⋅cm2). Possible sources of this fluctuation have been also discussed in this paper

show abstract

Structural and transport properties in alloyed Ti/Al Ohmic contacts formed on p-type Al-implanted 4H-SiC annealed at high temperature

Cited by 66 publications

References 40 publications

Effects of Annealing Treatments on the Properties of Al/Ti/p-GaN Interfaces for Normally OFF p-GaN HEMTs

Effects of Annealing Treatments on the Properties of Al/Ti/p-GaN Interfaces for Normally OFF p-GaN HEMTs

Effect of high temperature annealing (T > 1650 °C) on the morphological and electrical properties of p-type implanted 4H-SiC layers

Very low specific contact resistance measurements made on a highly p-type doped 4H-SiC layer selectively grown by vapor-liquid-solid transport

Contact Info

Product

Resources

About

Structural and transport properties in alloyed Ti/Al Ohmic contacts formed on p-type Al-implanted 4H-SiC annealed at high temperature

Cited by 66 publications

References 40 publications

Effects of Annealing Treatments on the Properties of Al/Ti/p-GaN Interfaces for Normally OFF p-GaN HEMTs

Effects of Annealing Treatments on the Properties of Al/Ti/p-GaN Interfaces for Normally OFF p-GaN HEMTs

Effect of high temperature annealing (T > 1650 °C) on the morphological and electrical properties of p-type implanted 4H-SiC layers

Very low specific contact resistance measurements made on a highly p-type doped 4H-SiC layer selectively grown by vapor-liquid-solid transport

Contact Info

Product

Resources

About

Effect of high temperature annealing (T > 1650 °C) on the morphological and electrical properties of p-type implanted 4H-SiC layers