RT doctoral thesis
T1 Hybrid-gate deep depletion mosfet high-k zro2/diamond-based power devices
A1 Soto Portillo, Beatriz
A2 Ciencia de los Materiales e Ingeniería Metalúrgica y Química Inorgánica
K1 electronic devices
K1 MOS capacitors
K1 diamond
AB The improvement of power electronic devices, making them durable and reliable in highpower environments is the key to the efficient low-carbon electrical energy production and distribution for our future energy system, eliminating the auxiliary systems and reducing the losses.Despite silicon is a well-established material it presents narrow and inadequate electricalcharacteristics to be use in power electronics. More efficient green electronic systems willbe reached by wide band gap or ultra wide band gap semiconductors since they can providelarger blocking capabilities, higher performance-cost ratios and they can reduce the thermalrequirements.Among the candidates, diamond is found to be the ultimate material to meet the powerelectronic trade-off between the on-resistance and the blocking capabilities. The ultra widebandgap (UWBG) of 5.5 eV leads to a non linear increase of the performance. The higher critical electric field (> 10 MV.cm−1) allows the use of higher doping concentrations comparingwith Si-technology. Which in combination with a superior bulk carrier mobility at room temperature for both electrons and holes (1060 cm2.V−1s−1and 2100 cm2.V−1s−1, respectively)favours the reduction of the devices’ resistance. Moreover, the resistivity will be reduced withincreasing temperature due to the deep dopants in diamond (ionization energies of B, P or Nof 0.38 eV, 0.58 eV and 1.7 eV, respectively), which result in incomplete ionization at roomtemperature.Likewise, the outstanding thermal conductivity (2200 W.m−1K−1) and the low concentration of intrinsic carriers (it is required a larger thermal energy to promote electrons from thevalence band to the conduction band than in semiconductors with smaller bandgap) make diamond the most suitable material for high temperature operation.The most widely used device whether in analog or digital circuits in the Electronic Industryis the metal-oxide-semiconductor field effect transistor (MOSFET). The focus will therefore beon this type of device, particularly based on diamond, which is also the subject of this thesis.However, the upgrade to the new generation of diamond-based power MOSFETs is limited.The main issues are caused by the lack of a native oxide that meets the demanding requirementsof the diamond interface. This latter degrades the performance of the devices and leads to apremature breakdown. And also by the difficulty of growing quality n-type diamond layers andthe lack of efficient p-channel devices comparable to their n-channel counterparts reached byother WBGSs. It is still challenging provide devices that exploit the diamond’s properties totheir full potential.This thesis proposes an alternative high-κ ZrO2/diamond-based hybrid-gate p-channel MOSFET taking advantage of the outstanding properties of these materials. In addition to the superior properties of diamond, mentioned above, zirconium dioxide contributes a barrier for holesof 2 eV, a critical electric field of 2 MV.cm−1, a high-enthalpy of formation and an excellentthermodynamic and thermal stability.An attempt has been made to correlate the electrical behaviour of the MOS structure withthe microstructural analysis. This has required an in-depth characterization that can be dividedResumen de la tesis viin two main blocks:• Materials characterization by the use of microscopy techniques such as high resolutiontransmission electron microscopy (HREM), energy dispersive X-ray spectroscopy (EDX)and valence electron energy loss spectroscopy (VEELS).• Fabrication and electrical characterization of the electronic devices through differentgrowth techniques (for both diamond and oxide thin films) such as microwave plasmaassisted chemical vapour deposition (MPACVD), physical vapour deposition (PVD) andatomic layer deposition (ALD); laser lithography, metals deposition using electron beam(ebeam) evaporation and various surface and thermal treatments to finally perform theelectrical measurements.In summary, this manuscript consists of the following chapters:• Chapter 1 will introduce the fabrication process methodology and state of the art of thediamond-based MOSFETs.• Chapter 2 is dedicated to the full analysis of the MOS capacitors, specially focus onunderstanding the behaviour of ZrO2 thin films.• Chapter 3 will deal with the implementation and characterization of this MOS structurein a novel hybrid-gate p-channel D3MOSFET.• The Overall conclusion and further outlook chapter will summarize the current status andwill provide future prospective for such electronic devices.
YR 2023
FD 2023
LK http://hdl.handle.net/10498/30339
UL http://hdl.handle.net/10498/30339
LA eng
DS Repositorio Institucional de la Universidad de Cádiz
RD 07-nov-2026