Monte Carlo model for the analysis and development of III-V Tunnel-FETs and Impact Ionization-MOSFETs

Impact-ionization metal-oxide-semiconductor FETs (I-MOSFETs) are in competition with tunnel FETs (TFETs) in order to achieve the best behaviour for low power logic circuits. Concretely, III-V I-MOSFETs are being explored as promising devices due to the proper reliability, since the impact ionization events happen away from the gate oxide, and the high cutoff frequency, due to high electron mobility. To facilitate the design process from the physical point of view, a Monte Carlo (MC) model which includes both impact ionization and band-to-band tunnel is presented. Two ungated InGaAs and InAlAs/InGaAs 100 nm PIN diodes have been simulated. In both devices, the tunnel processes are more frequent than impact ionizations, so that they are found to be appropriate for TFET structures and not for I-MOSFETs. According to our simulations, other narrow bandgap candidates for the III-V heterostructure, such as InAs or GaSb, and/or PININ structures must be considered for a correct I-MOSFET design

Temperature Behavior of Gunn Oscillations in Planar InGaAs Diodes

[EN]Planar Gunn diodes on In0.53Ga0.47 As with lengths between 2 and 5 μm have been fabricated and characterized in a temperature range of 10 to 300 K. Two different oscillation regimes are observed depending on temperature. At the higher values, the frequency of the oscillations decreases as the bias increases, as expected for a well-established transit-time domain mode. But below approximately 75 K, the behavior is the opposite, the frequency of the Gunn oscillations increases with the bias. This fact, together with a much lower amplitude of the oscillations, indicate the possible switch to a different oscillation mode in which the domains are not able to attain their complete maturation before reaching the anode.Spanish MINECO under Project TEC2017-83910-R and JCyL and FEDER under Project SA254P1

Comprehensive characterization of Gunn oscillations in In0.53Ga0.47As planar diodes

[EN]In this work, In0.53Ga0.47As planar Gunn diodes specifically designed for providing oscillations at frequencies below 30 GHz have been fabricated and characterized. Different types of measurements were used to define a set of consistent methods for the characterization of the oscillations that can be extended to the sub-THz frequency range. First, negative differential resistance and a current drop are found in the I–V curve, indicating the potential presence of Gunn oscillations (GOs), which is then confirmed by means of a vector network analyzer, used to measure both the S11 parameter and the noise power density. The onset of unstable GOs at applied voltages where the negative differential resistance is hardly visible in the I–V curve is evidenced by the observation of a noise bump at very low frequency for the same applied voltage range. Subsequently, the formation of stable oscillations with an almost constant frequency of 8.8 GHz is observed for voltages beyond the current drop. These results have been corroborated by measurements performed with a spectrum analyzer, which are fully consistent with the findings achieved by the other techniques, all of them applicable to Gunn diodes oscillating at much higher frequencies, even above 300 GHz.Spanish MINECO through project TEC2017-83910-R and the Junta de Castilla y León and FEDER through projects SA022U16 and SA254P18

Study and fabrication of III-V impact ionization MOSFET for low power applications

La réduction de la puissance consommée des transistors à effet de champ (MOSFETs) est un challenge pour le futur de la nanoélectronique. En 2025, l’Agence Internationale de l’Énergie (AIE) estime qu’il y aura environ 50 milliard d’objets autonomes et nomades nécessitant alors une faible puissance consommée. L’apparition de nouveaux dispositifs tels que les transistors à effet tunnel (TFETs) ou les transistors à ionisation par impact (I MOSFETs) permettra potentiellement de réduire la puissance consommée de ces objets. Dans ce travail de thèse, nous avons étudié pour la première fois le transistor à ionisation par impact à base de matériaux III V des filières arséniée et antimoniée. La structure pin, composant principal du I MOSFET, est tout d’abord étudiée. L’ensemble des briques technologiques des I MOSFET a ensuite été développé, et en particulier l’interface entre l’oxyde et le semiconducteur III-V qui a été optimisée par un traitement innovant par plasma d’oxygène (O2). Ce traitement a montré une amélioration de la qualité de l’interface oxyde/semiconducteur conduisant à une commande des charges beaucoup plus efficace. Pour finir, nous avons montré les études, fabrications et caractérisations d’un transistor à effet tunnel InGaAs et d’un I MOSFET GaSb présentant une architecture verticale où la grille est auto-alignée.The reduction in the power consumption of field effect transistors (MOSFETs) is a challenge for the future of nanoelectronics. By 2025, the International Energy Agency (IEA) estimates that there will be around 50 billion autonomous and nomadic objects requiring low power consumption. The appearance of new devices such as tunnel effect transistors (TFETs) or impact ionization transistors (I¬ MOSFETs) will potentially reduce the power consumption of these objects.In this thesis work, we studied for the first time the impact ionization transistor based on materials III-V, especially arsenic and antimony based materials. The pin structure, the main component of the I MOSFET, is first studied. We then developed all the process steps of the I-MOSFET fabrication, and in particular we optimized the interface between the oxide and the III-V semiconductor by an innovative treatment using oxygen plasma (O2). This special treatment has shown a clear improvement in charge control. Finally, we have shown studies, fabrications and characterizations of an InGaAs based TFET and a GaSb based I MOSFET with a vertical architecture, where the gate is self-aligned

Defect states in LaAlO3/SrTiO3 heterostructure using Deep-level Transient Fourier Spectroscopy

International audienc

Deep-Level Transient Fourier Spectroscopy (DLTFS) for the characterization of defect states in functional oxide-based devices

International audienc

Deep-Level Transient Fourier Spectroscopy (DLTFS) for the characterization of defect states in functional oxide-based devices

International audienc

Defect states in LaAlO3/SrTiO3 heterostructure using Deep-level Transient Fourier Spectroscopy

International audienc

Electrical characterization and extraction of activation energies of the defect states in the LaAlO₃/SrTiO₃ heterostructure

International audienceIn this work, we study the electronic properties of defects in the LaAlO3/SrTiO3 heterostructure, which is known to host a high mobility two-dimensional electron gas (2DEG) at the interface. This 2DEG also shows photoconductance, which could be related to defects that act as deep centers trapping and releasing carriers by interaction with light. This phenomenon has raised an interest for the identification of deep energy levels in the LaAlO3/SrTiO3 heterostructure. We have studied the defect state properties using electrical characterization such as capacitance-voltage (C-V), current-voltage (I-V) measurements and Deep-Level Transient Fourier Spectroscopy (DLTFS). From C-V and I-V analysis, a hysteresis was observed indicating an effect of mobile charges in the LaAlO3. Using DLTFS we identify three defect states located at around 0.17 eV below conduction band and at 0.23 eV and 0.26 eV above the valence band. These defect states were attributed to defects in SrTiO3 such as strontium vacancies or titanium vacancies. We identify a fourth defect state having an energy of about 0.69 eV below the conduction band that could be related to oxygen vacancies in LaAlO3 or in SrTiO3. In addition, the observation of an effect of the electric field with DLTFS indicated that oxygen vacancies might be involved in Fowler-Nordheim or trap-assisted tunneling through the LaAlO3 the layer

Persistent Photocarrier Accumulation and Depletion in LaAlO3/SrTiO3 Quantum Wells

International audienc