List of Figures

• 2.1. Comparison of saturated output power/mm gate width as a function of frequency.
• 2.2. Comparison of the absolute output power as a function of frequency.
• 2.3. Comparison of gain per stage as a function of frequency.
• 2.4. Comparison of the power added efficiency as a function of frequency.
• 2.5. Noise figure versus frequency for low noise amplifiers.
• 2.6. Comparison of $f_{T}$$\cdot$$l_{g}$ for different FET types.
• 2.7. Comparison of the $BV_{i}$ versus $f_{T}$ for MESFET, HEMT, and HBT taken from different material systems.
• 2.8. Power density versus frequency for GaN HEMTs circuits for different substrates and modes of operation.
• 2.9. Absolute output power as a function of frequency for GaAs HBTs and GaN HEMTs.
• 2.10.  $f_{T}$, $f_{max}$, and applied V$_{dd max}$ as a function of CMOS effective gate length according to ITRS 99 roadmap [252].
• 2.11. Reported output power versus frequency for several analog Si technologies.
• 2.12. $f_T$ as a function of $BC_{EO}$ for Si bipolar technologies.
• 2.13. $f_T$ as a function of $BC_{EO}$ for several published SiGe HBT technologies.
• 3.1. Standard terms for layers in a HEMT used in this work.
• 3.2. Bowing parameters for the band gap in Al$_x$Ga$_{1-x}$N [255,303].
• 3.3. Comparison of the analytical models and experimental data for ${\it N}_{\mathrm{D}}$= 5..10$\times$10$^{16}$ cm$^{-3}$ for Al$_{x}$Ga$_{1-x}$As.
• 3.4. Carrier mobility as a function of material composition for In$_x$Al$_{1-x}$As in comparison with measurements.
• 3.5. Carrier mobility as a function of material composition for In$_x$Ga$_{1-x}$As at ${\it T}_\mathrm{L}$= 300 K.
• 3.6. Comparison of the analytical model, measurement, and MC data for In$_{0.52}$Al$_{0.48}$As versus doping concentration at ${\it T}_\mathrm{L}$= 300 K [105,163].
• 3.7. Comparison of the analytical model, measurements, and MC data for In$_{0.53}$Ga$_{0.47}$As versus doping concentration at ${\it T}_\mathrm{L}$= 300 K.
• 3.8. Saturation velocity versus temperature for GaN and AlN [17,204].
• 3.9. Saturation velocity as a function of material composition for In$_x$Al$_{1-x}$As.
• 3.10. Saturation velocity as a function of material composition for In$_x$Ga$_{1-x}$As.
• 3.11. Saturation velocity versus material composition for Al$_x$Ga$_{1-x}$As.
• 3.12. Saturation velocity versus temperature for In$_{0.53}$Ga$_{0.47}$As [52,91,317].
• 3.13. Saturation velocity versus material composition for Al$_x$Ga$_{1-x}$N [17].
• 3.14. Fit of the measured impact ionization rates versus inverse field for GaAs [56].
• 3.15. Measured impact ionization rates versus inverse field for In$_{0.53}$Ga$_{0.47}$As [205,297].
• 3.16. Impact ionization parameters as a function of material composition for Al$_x$Ga$_{1-x}$As [221].
• 3.17. Impact ionization rates as a function of material composition for In$_x$Al$_{1-x}$As [60,91,221,309].
• 3.18. Impact ionization parameters versus temperature for a given field in GaAs [60].
• 3.19. Impact ionization parameters versus temperature in InP [285].
• 3.20. Modeling of the impact ionization rate vs. carrier temperature for GaAs with the lattice temperature $T_L$ as a parameter.
• 3.21. Modeling of the impact ionization rate vs. carrier temperature for In$_{0.53}$Ga$_{0.47}$As with the lattice temperature ${\it T}_\mathrm{L}$ as a parameter.
• 3.22. Modeling of the temperature dependence of the thermal conductivity of GaN, AlN, and SiC [260,266,267].
• 3.23. Typical carrier concentrations versus channel In content in In$_x$Ga$_{1-x}$As HEMTs obtained by Hall data at ${\it T}_\mathrm{L}$= 300 K.
• 3.24. Active doping density $n_{ac}$ versus nominal doping density $n_{nom}$.
• 3.25. Different ohmic contact situations.
• 3.26. Areas considered for a one- and two-dimensional treatment of the integration path for a high-power pseudomorphic HEMT.
• 3.27. Mean carrier velocities $v_{eff}$ as a function of gate length $l_g$.
• 3.28. Overshoot effects as a function of background doping.
• 3.29. Mid-channel velocity curve obtained by DAMOCLES for $V_{DS}$= 2 V, $V_{GS}$= 0 V and corresponding carrier concentration in mid-channel.
• 3.30. Three-dimensional energetic and local electron distribution obtained by using the simulator DAMOCLES.
• 3.31. Gate currents $I_G$ as a function of temperature $T_{sub}$ for an InP based InAlAs/InGaAs HEMT.
• 3.32. Two-dimensional HD impact ionization generation rates in a single recess AlGaAs/ InGaAs HEMT at $V_{DS}$= 1 V and $V_{DS}$= 5 V using MINIMOS-NT.
• 4.1. Standard small-signal equivalent circuit of a HEMT [36].
• 4.2. Extended small-signal equivalent circuit for a HEMT including gate-leakage and impact ionization [230].
• 4.3. $f_T$ as a function of $V_{DS}$ for an InAlAs/InGaAs/InP HEMT, an AlGaAs/InGaAs/GaAs PHEMT and a AlGaN/GaN HEMT.
• 4.4. $f_T$ as a function of $V_{DS}$ for several different AlGaAs/InGaAs/GaAs HEMT technologies.
• 4.5. Measured (+) and simulated (-) S-parameters between f= 2..120 GHz for $V_{DS}$= 1.5 V.
• 4.6. Program sketch of PALACE.
• 5.1. Definition of the mean device for a wafer map of output curve fields.
• 5.2. 4 inch wafer map results of a pseudomorphic AlGaAs/InGaAs HEMT.
• 5.3. Scree plot of the example.
• 5.4. Inclusion of external variables into the optimization process.
• 5.5. Sensitivity analysis of a $S_{21}$ towards $d_{gc}$ variations as a function of frequency.
• 6.1. Typical dimensions for 3D thermal chip and 2D electro-thermal device simulations.
• 6.2. Temperature distribution of a two-dimensional simulation for an on-wafer situation fitted to the boundaries obtained by three-dimensional simulation.
• 6.3. Output characteristics with the gate width as a parameter for devices from the same cell on the same wafer.
• 6.4. Transistor-transistor interaction: image of the transistor test structure.
• 6.5. $f_T$ as a function of dissipated power for the test structure.
• 6.6. Transistor-transistor interaction: $g_m$ at $T_{sub}$= 373 K for an 8$\times$125 $\mu$m HEMT as a function of $V_{GS}$ for transistors of the same kind switched in parallel.
• 6.7. Pulsed DC-measurements as a function of on pulse width for a repetition rate of 100 ms.
• 6.8. Current dependence of the breakdown voltage $BV_{DS}$ of Technology B, Variation A.
• 6.9. Current dependence of the breakdown voltage $BV_{DS}$ of Technology B, Variation B.
• 6.10. Current dependence of the breakdown voltage $BV_{DS}$ of Technology A.
• 6.11. Current dependence of the breakdown voltage $BV_{DS}$ of Technology C.
• 6.12. Temperature dependence of the breakdown voltages $BV_{GS}$ and $BV_{GD}$ of Technology B.
• 6.13. Temperature dependence of the breakdown voltage $BV_{DS}$ of the InP-based composite channel HEMT of Technology E.
• 6.14. Drain ledge dependence of the breakdown voltage $BV_{DS}$ for a gate current of$I_G$= 1 mA/mm of Technology D.
• 6.15. Breakdown voltage $BV_{DS}$ versus gate length $l_g$ of Technology D.
• 6.16. Temperature dependence of the breakdown voltage $BV_{DS}$ of Technology D.
• 6.17. Comparison of the 1/f noise between 0.5 Hz and 10 MHz for various transistor samples.
• 6.18. Load-pull measurement of P$_{sat}$, P$_{-1dB}$, and gain for 4$\times$60 $\mu$m HEMT versus frequency of Technology A.
• 6.19. Output power, gain, and PAE for f= 30 GHz, Technology B, Variation A.
• 6.20. Output power, gain, and PAE for f= 30 GHz, Technology B, Variation B.
• 6.21. Output power, gain, and PAE for f= 40 GHz for Variation B for $T_L$= 298 K and $T_L$= 343 K for a 6$\times$60 $\mu$m device.
• 6.22. Temperature dependence of the $P_sat$, P$_{-3dB}$, and P$_{-1dB}$ of a high-power amplifier at f= 35 GHz.
• 6.23. Load-pull measurement for a 8$\times$60 $\mu$m device of Technology C at $V_{DS}$= 3.0 V.
• 6.24. Output power, gain, and PAE for a 8$\times$60 $\mu$m at f= 35 GHz of Technology D.
• 6.25. Load-pull measurements for the same device at f= 40 GHz.
• 6.26. Saturated output power $P_{sat}$ and gain for f= 35 GHz for two different substrate temperatures $T_{sub}$.
• 6.27. Temperature dependence of the optimum load for a substrate temperature $T_{sub}$= 298 K and 353 K.
• 6.28. Saturated output power, gain, and PAE of a 8$\times$60 $\mu$m at f= 35 GHz versus relative recess length in Technology D.
• 6.29. Saturated output power $P_{sat}$ versus frequency, measured for Technology D for a second HEMT layout.
• 7.1. Three-dimensional image of critical simulation issues in HEMTs(1)=Thermal boundary conditions, (2)= Heterojunction carrier transport, (3)= ($\delta$-)doping activation, (4) = high field effects, (5) = gate currents.
• 7.2. Output characteristics for a $l_g$= 150 nm Al$_{0.2}$Ga$_{0.8}$As/In$_{0.2}$Ga$_{0.8}$As/GaAs HEMT.
• 7.3. $f_T$ versus gate length $l_g$ for $V_{DS}$= 1.5 V.
• 7.4. Transconductance $g_m$ versus lattice temperature $T_L$ including self-heating.
• 7.5. Threshold voltage $V_T$ versus $\delta$-doping concentration $l_g$= 440 nm.
• 7.6. Saturation current $I_{Dmax}$ as a function of $\delta$-doping concentration for $V_{DS}$= 2 V.
• 7.7. Simulated (-) and measured (+) S-parameters at $T_L$= 373 K and $V_{DS}$= 1.5 V and $V_{GS}$ for $g_{mmax}$.
• 7.8. Simulated (-) and measured (+) S-parameters at $T_L$= 300 K and $V_{DS}$= 2 V and $V_{GS}$= -0.5 V.
• 7.9. Simulated and measured $f_T$ and RF-$g_m$ as a function of $V_{GS}$ bias.
• 7.10. $C_{gs}$ and $C_{gd}$ as a function of $V_{DS}$ bias for constant $V_{GS}$.
• 7.11. $C_{gs}$ as a function of $V_{DS}$ without holes and with holes including generation/ recombination for a $l_g$= 140 nm pseudomorphic HEMT.
• 7.12. Simulated $C_{gd}$ as a function of $V_{DS}$ bias for $l_g$= 440 nm with the cap doping concentration as parameter.
• 7.13. Simulated and measured RF-$g_{ds}$ as a function of bias $V_{GS}$ for $V_{DS}$= 2 V.
• 7.14. $\tau$ as a function of $V_{GS}$ bias for $V_{DS}$= 2 V.
• 7.15. The drain-source capacitance $C_{ds}$ as a function of $V_{GS}$ bias for $V_{DS}$= 2 V.
• 7.16. Experimental decrease of $\Delta f_T$/ $\Delta V_{DS}$ as a function of gate length $l_g$.
• 7.17. $f_T$ as a function of $V_{DS}$ bias for different contact situations.
• 7.18. $f_c$ as a function of $C_{gd}$ for 4$\times$40 $\mu$m device.
• 7.19. Modeled $f_c$ as a function of gate-to-channel separation $d_{gc}$.
• 7.20. Output characteristics of pseudomorphic power HEMT.
• 7.21. Measured and simulated $f_T$ as a function of $V_{DS}$ bias.
• 7.22. Measured transconductance $g_m$ versus $V_{GS}$  at $V_{DS}$=1.5 V and different $T_L$ for a 4$\times 40$ $\mu$m high-power AlGaAs/InGaAs HEMT.
• 7.23. Geometry for a double recess.
• 7.24. Electric field for $V_{DS}$= 5 V, $V_{DS}$= 8 V and $I_D$$\approx$ 250 mA/mm for a $l_g$= 190 nm HEMT with a depleted recess.
• 7.25. Electric field for $V_{DS}$= 5 V, $V_{DS}$= 8 V and $I_D$$\approx$ 250 mA/mm for a $l_g$= 190 nm HEMT with a non-depleted outer recess.
• 7.26. Two-dimensional view of the carrier concentration in [cm$^{-3}$] for a HEMT for $V_{DS}$= 5 V and $I_D$= 150 mA/mm.
• 7.27. Maximum electric field for an open device ($I_D$= 250 mA/mm) as a function of inner recess length $l_R$ for a non-depleted recess concept.
• 7.28. Electric field for two different surface potentials for $V_{DS}$= 17 V for a $l_g$= 300 nm pseudomorphic HEMT.
• 7.29. $f_T$ versus recess length $l_R$ for $V_{DS}$= 1.5 V and 5 V.
• 7.30. Measured drop $\Delta$ $f_T$/$\Delta$$V_{DS}$  versus  $T_{sub}$.
• 7.31. Output characteristics of a 2$\times$60 $\mu$m pseudomorphic AlGaAs/InGaAs/GaAs HEMT.
• 7.32. Transconductance $g_m$ versus $V_{GS}$ for a $l_g$= 100 nm GaAs MESFET [185].
• 7.33. Output characteristics of a $l_g$= 300 nm based AlGaAs/InGaAs HEMT on GaAs substrate.
• 7.34. Measured temperature dependence of $g_m$ and $f_T$ for $T_L$= 300-473 K for a $l_g$= 150 nm device.
• 7.35. Simulated and measured transfer characteristic as a function of temperature $T_{sub}$.
• 7.36. Output characteristics of a dual channel InP based pseudomorphic HEMT with $l_g$= 150 nm.
• 7.37. Simulated and measured input characteristics $I_G$ versus $V_{GS}$.
• 7.38. Input characteristics $I_G$ versus $V_{GS}$ as a function of temperature $T_{sub}$.
• 7.39. Simulated (-) and measured (+) S-parameters of a dual channel InP HEMT with $l_g$= 150 nm.
• 7.40. Simulated and measured $f_T$  versus $V_{DS}$  bias at constant $V_{GS}$ for the $l_g$= 150 nm dual channel InP based HEMT.
• 7.41. Transfer characteristics of a metamorphic depletion-type HEMT with $l_g$= 150 nm.
• 7.42. Transconductance $g_m$ versus $V_{GS}$ of a $l_g$= 400 nm metamorphic HEMT.
• 7.43. $f_T$ as a function of material composition.
• 7.44. Transfer characteristics of an enhancement-type InAlAs/InGaAs HEMT for two $V_{DS}$ bias.
• 7.45. $C_{gd}$ reduction of a $l_g$= 150 nm HEMT versus average $eps_r$.
• 7.46. Threshold voltage $V_T$ versus gate-to-channel separation $d_{gc}$.
• 7.47. Threshold voltage $V_T$  versus $\delta$-doping concentration.
• 7.48. $f_T$ versus $V_{DS}$ in the low-power range.
• 7.49. $f_T$ versus gate length $l_g$.
• 7.50. Simulated and measured transfer characteristics for $V_{DS}$= 6 V for a $l_g$= 200 nm AlGaN/GaN HEMT.
• A.1. Active load-pull system for 26.5-40 GHz.