Enhancement-mode power heterojunction FET utilizingAl0.5Ga0.5As barrier layer with negligibleoperation gate current for digital cellular phones

We have developed a novel enhancement-mode double-doped AlGaAs/InGaAs/AlGaAs heterojunction FET (HJFET) with a 5 nm thick Al_0.5Ga_0.5As barrier layer inserted between an In _0.2Ga_0.8As channel layer and an upper Al_0.2 Ga_0.8As electron supply layer. The Al_0.5Ga _0.5As barrier layer reduces gate current under high forward gate bias voltage, resulting in a high forward gate turn-on voltage (V _F) of 0.87 V, which is 170 mV higher than that of an HJFET without the barrier layer. Suppression of gate current assisted by a parallel conduction path in the upper electron supply layer was found to be also important for achieving the high V_F. The developed device exhibited a high maximum drain current of 300 mA/mm with a threshold voltage of 0.17 V. A 950 MHz PDC power performance was evaluated under single 3.5 V operation. An HJFET with a 0.5 μm long gate exhibited 0.92 W output power and 63.6% power-added efficiency with 0.08 mA gate current (I_g) at -48 dBc adjacent channel leakage power at 50 kHz off-center frequency. This I_g is one-thirteenth to that of the HJFET without the barrier layer. These results indicate that the developed enhancement-mode HJFET is suitable for single low voltage operation power applications     

High performance BCB-bridged AlGaAs/InGaAs power HFETs

A novel low-k benzocyclobutene (BCB) bridged and passivated layer for AlGaAs/InGaAs doped-channel power field effect transistors (FETs) with high reliability and linearity has been developed and characterized. In this study, we applied a low-k BCB-bridged interlayer to replace the conventional air-bridged process and the SiN/sub x/ passivation technology of the 1 mm-wide power device fabrication. This novel and easy technique demonstrates a low power gain degradation under a high input power swing, and exhibits an improved adjacent channel power ratio (ACPR) than those of the air-bridged one, due to its lower gate leakage current. The power gain degradation ratio of BCB-bridged devices under a high input power operation (P/sub in/ = 5 /spl sim/ 10 dBm) is 0.51 dB/dBm, and this value is 0.65 dB/dBm of the conventional air-bridged device. Furthermore, this novel technology has been qualified by using the 85-85 industrial specification (temperature = 85 C, humidity = 85%) for 500 h. These results demonstrate a robust doped-channel HFET power device with a BCB passivation and bridged technology of future power device applications.     

BCB-bridged distributed wideband SPST switch using 0.25-/spl mu/m In/sub 0.5/Al/sub 0.5/As--In/sub 0.5/Ga/sub 0.5/As metamorphic HEMTs

In/sub 0.5/Al/sub 0.5/As--In/sub 0.5/Ga/sub 0.5/As metamorphic high-electron mobility transistor (mHEMT) dc-30 GHz distributed single-pole-single through (SPST) switches were designed and fabricated using the low-/spl kappa/ benzocyclobutene (BCB) bridged technology. The current gain cutoff frequency, and the electron transit time of In/sub 0.5/Al/sub 0.5/As--In/sub 0.5/Ga/sub 0.5/As mHEMTs have been investigated. By analyzing the extrinsic total delay time, the effective velocity of electrons can be estimated, and the average velocity is 2.3/spl times/10/sup 7/cm/s. The dc-30 GHz distributed wideband SPST switch exhibits an insertion loss of less than 5.5 dB, and an isolation larger than 30 dB, which is the first demonstration of the high-isolation of InAlAs-InGaAs mHEMTs monolithic switch. As to the power performance, this switch can handle the power up to 12 dBm at 2.4 GHz. After over 250 h of 85-85 (temperature =85/spl deg/C, humidity =85%) environmental evaluation, this BCB passivated and bridged microwave and monolithic integrated circuit switch demonstrates reliable RF characteristics without any significant performance change, which proves that this process using the low-/spl kappa/ BCB layer is attractive for millimeter-wave circuit applications.     

Device linearity comparisons between doped-channel andmodulation-doped designs in pseudomorphic Al0.3Ga0.7As/In0.2Ga0.8As heterostructures

The linearities of pseudomorphic Al_0.3Ga_0.7As/In_0.2Ga_0.8As doped-channel FET's were characterized by comparing the characteristics of modulation-doped field-effect transistors (FET's) based on dc and microwave evaluations. By using an undoped high-bandgap layer beneath the gate, the so-called parasitic MESFET-type conduction, which is common in HEMT's, can therefore be eliminated in doped-channel designs. Therefore, a wide and flat device performance together with a high current driving capability can be achieved in DCFET's. This linearity improvement in device performance suggests that doped-channel designs are more suitable for application in microwave power devices     

Highly sensitive In0.53Ga0.47As/InP Hallsensors grown by MOVPE

High performance InP/InGaAs Hall sensors appropriate for applications requiring high sensitivity at low power dissipation, good linearity, low temperature sensitivity, and high resolution are reported. The layer structures grown by MOVPE combine a high mobility In _0.53Ga_0.47As channel with isolation by semi-insulating InP. With this design bias current related sensitivities up to 760 V/AT at sheet resistances below 840 Ω/square have been achieved, allowing high output signals at low power dissipation. Due to the active layer isolation by semi-insulating InP, bias currents are not limited by channel pinch-off or junction breakdown. This leads to absolute sensitivities as high as 12.5 V/T. Linearity errors are lower than -0.8% up to magnetic fields of 0.5 T. Temperature coefficients of the sensitivity were measured for different donor concentrations of the active layer. The lowest value of -0.07%/K was found for a doping of 10 ¹⁶ cm^-3, in accordance with theoretical predictions. High signal-to-noise ratios corresponding to minimal detectable fields of 50 nT/Hz^l/2 and 160 nT/Hz^l/2, respectively, were measured at 1 kHz and 100 Hz     

0.2-/spl mu/m gate-length InGaP-InGaAs DCFETs for C-band MMIC amplifier applications

A C-band In/sub 0.49/Ga/sub 0.51/P-In/sub 0.15/Ga/sub 0.85/As doped-channel FET (DCFET) monolithic power amplifier was designed and fabricated using low-k benzocyclobutene (BCB) interlayer technology. With a photosensitive low-k BCB interlayer (/spl epsiv/=2.7), not only can the circuit's passivation layer, but also the capacitor insulator, via holes, and bridge process be realized simultaneously, where the process complexity and cost can be reduced. In addition, a 0.2-/spl mu/m T-shaped gate InGaP-InGaAs doped-channel FET with a high current density and a high linearity is introduced to the amplifier using the e-beam lithography. This C-band power amplifier can achieve a linear power gain of 9.3 dB and an output power of 15.3 dBm, which proves that this novel MMIC process using low-k BCB interlayer technology is attractive for microwave and millimeter wave circuit applications.     

Ion-implanted In(x)Ga(1-x)As MESFET's on GaAssubstrate for low-cost millimeter-wave IC application

Ion-implanted In_(x)Ga_(1-x) As MESFETs on GaAs substrate are very attractive devices for ultra-high-frequency and ultra-high-speed integrated circuit applications due to the simplicity of material structure and manufacturability of ion implantation technology. The advances in ion-implanted In_(x)Ga_(1-x) As/GaAs MESFET technology are reviewed, focusing on material structures, device fabrications, manufacturability, current gain cutoff frequency, and maximum power oscillation frequency performance, as well as low noise, power, and oscillator performance in the millimeter-wave frequency range     

Uniform, high-gain AlGaAs/In0.05Ga0.95As/GaAsP-n-p heterojunction bipolar transistors by dual selective etch process

AlGaAs/InGaAs/GaAs P-n-p heterojunction bipolar transistors (HBTs) have been fabricated using a dual selective etch process. In this process, a thin AlGaAs surface passivation layer surrounding the emitter is defined by selective etching of the GaAs cap layer. The InGaAs base is then exposed by selective etching of the AlGaAs emitter. The resulting devices were very uniform, with current gain varying by less than ±10% for a given device size. Current gain at a given emitter current density was independent of device size, with gains of over 200 obtained at current densities above 5×10⁴ A/cm ²     

High-performance In0.52Al0.48As/In0.53Ga0.47As HFET compatible with optical-detectorintegration

The authors report the successful demonstration of a 1.0-μm gate InAlAs/InGaAs heterojunction FET (HFET) on top of thick InGaAs layers using lattice-matched molecular beam epitaxy (MBE). This scheme is compatible with metal-semiconductor-metal (MSM) photodetector fabrication. The authors measured the performance of InAlAs/InGaAs HFETs from 0 to 40 GHz. Device performance is characterized by peak extrinsic transconductances of 390 mS/mm and as-measured cutoff frequencies up to 30 GHz for a nominal 1.0-μm-gate-length HFET. HFET device measurements are compared for samples growth with and without the thick underlying InGaAs optical-detector absorbing layer     

Influence of quantum-well width on device performance ofAl0.30Ga0.70As/In0.25Ga0.75As (on GaAs) MODFETs

An experimental study in which the quantum well width (W) is varied from 45 to 200 Å is discussed. Optimum device performance was observed at a well width of 120 Å. The 0.2-μm×130-μm devices with 120-Å quantum-well width typically exhibit a maximum channel current density of 550 mA/mm, peak transconductance of 550 mS/mm, and peak current gain cutoff frequency ( f_T) of 122 GHz. These results have been further improved in subsequent fabrications employing a trilevel-resist mushroom-gate process. The 0.2-μm×50-μm devices with mushroom gate exhibit a peak transconductance of 640 mS/mm, peak f _T of 100 GHz, and best power gains cutoff frequency in excess of 200 GHz. These results are among the best ever reported for GaAs-based FETs and are attributed to the high two-dimensional electron gas (2DEG) sheet density, good low-field mobility, low ohmic contact, and the optimized mushroom gate process     

In0.53Ga0.47As/In0.52Al0.48As雪崩光电二极管的数值模拟研究

建立了SACM型In0.53Ga0.47As/In0.52Al0.48As雪崩光电二极管(APD)的分析模型,通过数值研究和理论分析设计出高性能的In0.53Ga0.47As/In0.52Al0.48As APD。器件设计中,一方面添加了In0.52Al0.48As势垒层来阻挡接触层的少数载流子的扩散,进而减小暗电流的产生;另一方面,雪崩倍增区采用双层掺杂结构设计,优化了器件倍增区的电场梯度分布。最后,利用ATLAS软件较系统地研究并分析了雪崩倍增层、电荷层以及吸收层的掺杂水平和厚度对器件电场分布、击穿电压、IV特性和直流增益的影响。优化后APD的单位增益可以达到0.9 A/W,在工作电压(0.9 Vb)下增益为23.4,工作暗电流也仅是纳安级别(@0.9 Vb)。由于In0.52Al0.48As材料的电子与空穴的碰撞离化率比InP材料的差异更大,因此器件的噪声因子也较低。     

Double-dopedIn0.35Al0.65As/In0.35Ga0.65As power heterojunction FET on GaAs substrate with 1 W outputpower

A double-doped metamorphic In_0.35Al_0.65As/In _0.35Ga_0.65As power heterojunction FET (HJFET) on GaAs substrate is demonstrated. The HJFET exhibits good dc characteristics, with gate forward turn on voltage of 1.0 V, breakdown voltage of 20 V, and maximum drain current of 490 mA/mm. Under RF operation at a frequency of 950 MHz, a power added efficiency of 63% with associated output power of 31.7 dBm is obtained at a gate width of 12.8 mm. This large gate width and state-of-the-art power performance in metamorphic HJFETS were enabled by a selective etching, sputtered WSi gate process and low surface roughness due to an Al_0.60Ga_0.40As_0.69Sb_0.31 strain relief buffer     

Performance of interface engineeredSiNx/ICL/InP/In0.53Ga0.47As/InP dopedchannel HIGFET's

SiN_x/InP/InGaAs doped channel passivated heterojunction insulated gate field effect transistors (HIGFETs) have been fabricated for the first time using an improved In-S interface control layer (ICL). The insulated gate HIGFETs exhibit very low gate leakage (10 nA@V_GS =±5 V) and I_DS (sat) of 250 mA/mm. The doped channel improves the DC characteristics and the HIGFETs show transconductance of 140-150 mS/mm (L_g=2 μm), f_t of 5-6 GHz (L_g=3 μm), and power gain of 14.2 dB at 3 GHz. The ICL HIGFET technology is promising for high frequency applications     

Effects of surface passivation during atomic layer deposition of Al2O3 on In0.53Ga0.47As substrates

In this work we investigate the effect of different III-V surface passivation strategies during atomic layer deposition of Al₂O₃. X-ray photoelectron spectroscopy indicates that bare As-decapped and sulfur passivated In_0.53Ga_0.47As present residual oxides on the surface just before the beginning of the Al₂O₃ deposition while the insertion of a Ge interface passivation layer results in an almost oxide free Ge/III-V interface. The study of the initial growth regimes, by means of in situ spectroscopic ellipsometry, shows that the growth of Al₂O₃ on Ge leads to an enhanced initial growth accompanied by the formation of Ge-O-Al species thus affecting the final electrical properties of the stack. Alternatively, deposition on decapped and S-passivated In_0.53Ga_0.47As results in a more controlled growth process. The sulfur passivation leads to a better electrical response of the capacitor that can be associated to a lower oxide/semiconductor interface trap density.     

Thermal analysis of bond layer influence on performance of an all-active vertically coupled, microring resonating laser

The vertical coupling of active InP based ring resonators and passive feeding waveguides necessitates the use of a waferbonding technology in the fabrication process. The required bond material (BCB) has a low thermal conductivity and will strongly influence the operating temperature and thus the performance of the ring resonator through its insulating effect. A comprehensive thermal analysis of a proposed vertically coupled ring resonator of 50 μm outer radius is undertaken during the design phase to determine the thermal impact of: the design of the wafer bond, the design of the passivation layer and the optical power levels. Thermal abatement strategies for semiconductor lasers are presented.     

Buried-Pt gate InP/In0.52Al0.48As/In0.7Ga0.3As pseudomorphic HEMTs

InP-based high electron mobility transistors (HEMTs) were fabricated by depositing Pt-based multilayer metallization on top of a 6-nm-thick InP etch stop layer and then applying a post-annealing process. The performances of the fabricated 55-nm-gate HEMTs before and after the post-annealing were characterized and were compared to investigate the effect of the penetration of Pt through the very thin InP etch stop layer. After annealing at 250 °C for 5 min, the extrinsic transconductance (G_m) was increased from 1.05 to 1.17 S/mm and Schottky barrier height was increased from 0.63 to 0.66 eV. The unity current gain cutoff frequency (f_T) was increased from 351 to 408 GHz, and the maximum oscillation frequency (f_max) was increased from 225 to 260 GHz. These performance improvements can be attributed to penetration of the Pt through the 6-nm thick InP layer, and making contact on the InAlAs layer. The STEM image of the annealed device clearly shows that the Pt atoms contacted the InAlAs layer after penetrating through the InP layer.     

Ga0.47In0.53As metal-semiconductor-metalphotodiodes using a lattice mismatchedAl0.4Ga0.6As Schottky assist layer

Metal-semiconductor-metal photodiodes (MSM PDs) with Ga_0.47 In_0.53As active layers were fabricated. The low Schottky barrier height of GaInAs was overcome by the insertion of a lattice mismatched AlGaAs intermediary layer between metal and GaInAs active layer. Fabricated MSM PDs utilising interdigitated metal electrodes formed by a self-alignment technique showed a fast rise and fall time of 650 ps, which was limited by the capacitance of the device. The gain of the device was less than 1     

22 nm In0.75Ga0.25As channel-based HEMTs on InP/GaAs substrates for future THz applications

In this work, the performance of L_g=22 nm In_0.75Ga_0.25As channel-based high electron mobility transistor (HEMT) on InP substrate is compared with metamorphic high electron mobility transistor (MHEMT) on GaAs substrate. The devices features heavily doped In_0.6Ga_0.4As source/drain (S/D) regions, Si double δ-doping planar sheets on either side of the In_0.75Ga_0.25As channel layer to enhance the transconductance, and buried Pt metal gate technology for reducing short channel effects. The TCAD simulation results show that the InP HEMT performance is superior to GaAs MHEMT in terms of f_T, f_max and transconductance (g_{m_max}). The 22 nm InP HEMT shows an f_T of 733 GHz and an f_max of 1340 GHz where as in GaAs MHEMT it is 644 GHz and 924 GHz, respectively. InGaAs channel-based HEMTs on InP/GaAs substrates are suitable for future sub-millimeter and millimeter wave applications.     

Device linearity improvement byAl0.3Ga0.7As/In0.2Ga0.8Asheterostructure doped-channel FETs

The linearities of pseudomorphic heterostructure Al_0.3Ga_0.7As/In_0.2Ga_0.8As doped-channel FETs (DCFETs) and HEMTs were evaluated by DC and RF testings. Due to the absence of parallel conduction in the doped-channel approach, as compared to the modulation-doped structure, a wide and flat device performance together with a high current density was achieved. This improvement of device linearity suggests that doped-channel designs are suitable for high frequency power device application     

Al2O3 stacks on In0.53Ga0.47As substrates: In situ investigation of the interface

In this work we present an in situ investigation of the interface composition between an In_0.53Ga_0.47As substrate and an Al₂O₃ oxide grown by molecular beam deposition in ultra high vacuum conditions. In the effort to improve the chemical quality of the interface, reduction of semiconductor-oxygen bonding at the interface can be obtained by growing a few Å thick pure Al layer before starting exposure of the surface to the atomic oxygen flux. Conversely, when a Ge interface passivation layer is intercalated between the semiconductor and the oxide stack, the interface chemistry is governed by Ge reaction with other species (Al, O), leading only to a partial suppression of the interface oxides.