Determination of the electron concentration and mobility in the vicinity of a quantum well and δ-doped layer in InGaAs/GaAs heterostructures

Comparative admittance measurements in mesadiodes on an n ⁺-GaAs substrate and in ring planar diode structures on an i-GaAs substrate, which contain a Si ??-doped layer and an InGaAs quantum well in the GaAs epitaxial layer are performed. The possibility of determining the concentration profile and electron mobility in the vicinity of the ??-doped layer and the InGaAs quantum well is shown based on an analysis of the simultaneously measured capacitance-voltage and conductance-voltage characteristics of the mesadiodes. By performing such measurements for i-GaAs-based ring diode structures with the given geometry, it is possible to reliably determine only the concentration profile. The influence of the relative location of the quantum well and ??-doped layer on the concentration profile and mobility is revealed. The phenomenon of Maxwell relaxation in i-GaAs-based ring diode structures is discussed.     

Effect of structural parameters on InGaAs/InAlAs 2DEG transport characteristics

The effect of structural parameters on the transport characteristics from 15 to 300 K of molecular beam epitaxy-grown InGaAs/InAlAs two dimensional electron gas structures lattice-matched to InP is determined. The InAlAs buffer layer thickness was varied from 1000 to 10,000Å. One sample also incorporated a InGaAs/InAlAs superlattice. The buffer layer thickness and structure had almost no effect on the mobility or sheet density. The InAlAs spacer layer was varied from 25 to 200Å. Increases in the InAlAs spacer thickness resulted in a monotonically decreasing sheet density and a peak in the mobility versus spacer thickness at 100Å. The highest 77 K mobility was 66,700 cm²/V/sds withN _D =1.2×10¹² cm^?2. The effect of illumination and temperature on the sheet concentration in these structures as well as on “bulk” InAlAs:Si was much smaller than in Al _x Ga_1?x As/GaAs structures or “bulk” Al _x Ga_1?x As, forx?0.30, indicating that devices based on this material system will not be characterized by many of the device instabilities observed in the AlGaAs/GaAs system.     

Extremely high gain 0.15 mu m gate-length InAlAs/InGaAs/InP HEMTs

High electron mobility transistors (HEMTs) based on the InAlAs/InGaAs heterojunction grown lattice matched to InP were fabricated with 0.15 mu m T-shaped gates. The use of an undoped InGaAs cap layer in the epitaxial structure leads to excellent gate characteristics and very high transistor gain. At 95 GHz, a maximum available gain of 13.6 dB was measured. A maximum frequency of oscillation f/sub max/ of 455 GHz was obtained by extrapolating from 95 GHz at -6 dB/octave. This is the best reported gain performance for any transistor.<>     

Planar-doped n-type InAlAs/InGaAs MODFETs on InP(311)A substratesby molecular beam epitaxy

N-type doping of silicon in InAlAs/InGaAs/InP modulation-doped field effect transistor (MODFET) structures grown by molecular beam epitaxy (MBE) for the (311)A orientation has been achieved by using the planar-doping technique. An electron mobility as high as 50000 cm² V-s with a sheet carrier concentration of 1.9×10¹²/cm² at 77 K is reported. MODFETs with 1.2-μm gate length exhibit an extrinsic transconductance of 400 mS/mm and a maximum drain current of 485 mA/mm. The results are comparable to those of MODFETs grown on (100) InP substrates. The results point to the possibility of making p-n multi layer structures with all-silicon doping     

Transistor performance and electron transport properties of highperformance InAs quantum-well FET's

A novel field-effect transistor based on a pseudomorphic InAs quantum well in a doped InGaAs/InAlAs double heterostructure is reported. Low-field mobility, electron peak velocity, and transistor performance are studied as functions of InAs quantum well thickness, where the InAs layer is in the center of a 300-Å uniformly doped InGaAs/InAlAs quantum well lattice matched to InP. Electron transport-both at low and high fields-along with transistor transconductance are optimal for structures with a 30-Å InAs quantum well. Transistors based on the InAs quantum well structures with 0.5-μm gate lengths yielded room temperature extrinsic transconductances of 708 mS/mm, more than a 100% increase over those with no InAs     

Effect of impact ionization in the InGaAs absorber on excess noise of avalanche photodiodes

The effects of impact ionization in the InGaAs absorption layer on the multiplication, excess noise and breakdown voltage are modeled for avalanche photodiodes (APDs), both with InP and with InAlAs multiplication regions. The calculations allow for dead space effects and for the low field electron ionization observed in InGaAs. The results confirm that impact ionization in the InGaAs absorption layer increases the excess noise in InP APDs and that the effect imposes tight constraints on the doping of the charge control layer if avalanche noise is to be minimized. However, the excess noise of InAlAs APDs is predicted to be reduced by impact ionization in the InGaAs layer. Furthermore the breakdown voltage of InAlAs APDs is less sensitive to ionization in the InGaAs layer and these results increase tolerance to doping variations in the field control layer.     

Emission of Terahertz Radiation from Two-Dimensional Electron Systems in Semiconductor Nano- and Hetero-Structures

This paper reviews recent advances in emission of terahertz radiation from two-dimensional (2D) electron systems in semiconductor nano-heterostructures. 2D plasmon resonance is first presented to demonstrate intense broadband terahertz emission from InGaP/InGaAs/GaAs and InAlAs/InGaAs/InP material systems. The device structure is based on a high-electron mobility transistor and incorporates the author??s original interdigitated dual-grating gates. Second topic focuses on graphene, a monolayer carbon-atomic honeycomb lattice crystal, exhibiting unique carrier transport and optical properties owing to massless and gapless energy spectrum. Coherent stimulated terahertz emission from femtosecond infrared-laser pumped epitaxial graphene is experimentally observed, reflecting the occurrence of negative dynamic conductivity and population inversion.     

A new extrinsic dc model for high speed lattice matched InAlAs/InGaAs/InP HEMT with a predicted 135 GHz cut-off frequency

Extrinsic lattice matched InAlAs/InGaAs/InP HEMT model, incorporating the parasitic source and drain resistance, for very high frequency application is developed. The current voltage characteristics and the transconductance have been evaluated and the influence of carrier concentration dependent mobility on frequency has also been analyzed. A cut-off frequency of 135 GHz is obtained.     

InGaAs/InGaAlAs MQW lasers with InGaAsP guiding layers grown by gas source molecular beam epitaxy

An InGaAs/InGaAlAs multiple-quantum-well (MQW) laser was grown by gas source molecular beam epitaxy (GS-MBE). The laser has InP cladding layers and InGaAsP guiding layers, and the active layer is composed of an InGaAs/InGaAlAs MQW layer. Electrons are injected into the MQW active layer by tunneling through the barriers. The threshold current of the InGaAs/InAlAs buried-heterostructure (BH)-MQW lasers was as low as 9.6 mA. The relaxation oscillation frequency of the InGaAs/InAlAs MQW lasers was found to be larger than that of the InGaAs/InGaAsP MQW lasers with the same structure.<>     

Digital integrated circuit using integrated InAlAs/InGaAs/InP HEMTsand InAs/AlSb/GaSb RITDs

The demonstration of the first integrated circuit using monolithically integrated InAs/AlSb/GaSb resonant interband tunnelling diodes (RITDs) and InAlAs/InGaAs/InP high electron mobility transistors (HEMTs) is reported. A D-flip-flop (D-FF) was implemented using the monostable/bistable logic element (MOBILE) circuit architecture, with a measured effective voltage gain in excess of 380. Power dissipation of less than 2.8 mW/gate was measured     

Hooge parameter of InGaAs bulk material and InGaAs 2DEG quantum well structures based on InP substrates

The 1/f noise of various InGaAs layers lattice matched to InP is investigated systematically at room temperature. To elucidate the origin of the 1/f noise in this type of III–V compound semiconductor, thick n-type doped InGaAs layers, typical InP based InAlAs/InGaAs or InP/InGaAs heterostrucuture field-effect transistor (HFET) structures, respectively, as well as InP based InAlAs/InGaAs quantum well structures with doped InGaAs two-dimensional electron gas (2DEG) channel are analysed. From the experiments it is found that mobility fluctuation is the only origin for the 1/f noise observed both in InGaAs bulk material and in 2DEG heterostructures of high quality. A Hooge parameter attributed to phonon scattering α_Hphon in the bulk material is found to be about 7×10⁻⁶ and agrees with those obtained from HFET structures with the highest mobilities (α_H≈1.5×10⁻⁵). Furthermore, the Hooge parameter of 2DEG structures strongly depends on the channel design and on the doping concentration in the n-type doped 2DEG channels.     

Interrelation of the construction of the metamorphic InAlAs/InGaAs nanoheterostructures with the InAs content in the active layer of 76–100% with their surface morphology and electrical properties

The influence of the construction of a metamorphic buffer on the surface morphology and electrical properties of InAlAs/InGaAs/InAlAs nanoheterostructures with InAs content in the active layer from 76 to 100% with the use of the GaAs and InP substrates is studied. It is shown that such parameters as the electron mobility and the concentration, as well as the root-mean-square surface roughness, substantially depend on the construction of the metamorphic buffer. It is established experimentally that these parameters largely depend on the maximal local gradient of the lattice constant of the metamorphic buffer in the growth direction of the layers rather than on its average value. It is shown that, with selection of the construction of the metamorphic buffer, it is possible to form nanostructured surfaces with a large-periodic profile.     

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.     

高电子迁移率晶体管新结构

介绍了通过插入ＩｎＡｓ层到ＩｎＧａＡｓ沟道中，改善了ＩｎＡｌＡｓ／ＩｎＧａＡｓ高电子迁移率晶体管（ＨＥＭＴ）的性质，合适的ＩｎＡｓ层厚度和准确的插入位置会使在３００Ｋ时此结构的ＨＥＭＴ比普通结构的ＨＥＭＴ的迁移率和电子速度分别提高３０％和１５％。     

Super-flat (411)A interfaces and uniformly corrugated (775)B interfaces in GaAs/AlGaAs and InGaAs/InAlAs heterostructures grown by molecular beam epitaxy

Extremely flat interfaces, i.e. effectively atomically flat interfaces over a wafer-size area were realized in GaAs/AlGaAs quantum wells (QWs) grown on (411)A GaAs substrates by molecular beam epitaxy (MBE). These flat interfaces are called as “(411)A super-flat interfaces”. Besides in GaAs/AlGaAs QWs, the (411)A super-flat interfaces were formed in pseudomorphic InGaAs/AlGaAs QWs on GaAs substrates and in pseudomorphic and lattice-matched InGaAs/InAlAs QWs on InP substrates. GaAs/AlGaAs resonant tunneling diodes and InGaAs/InAlAs HEMT structures with the (411)A super-flat interfaces were confirmed to exhibit improved characteristics, indicating high potential of applications of the (411)A super-flat interfaces. High density, high uniformity and good optical quality were achieved in (775)B GaAs/(GaAs)_m(AlAs)_n quantum wires (QWRs) self-organized in a GaAs/(GaAs)_m(AlAs)_n QW grown on (775)B GaAs substrates by MBE. The QWRs were successfully applied to QWR lasers, which oscillated at room temperature for the first time as QWR lasers with a self-organized QWR structure in its active region. These results suggest that MBE growth on high index crystal plane such as (411)A or (775)B is very promising for developing novel semiconductor materials for future electron devices.     

InGaAs(InAlAs)/InP和InP/InAlAs湿法选择腐蚀研究

介绍了两种选择腐蚀液对InGaAs(InAlAs)I/nP和InPI/nAlAs异质结构材料选择腐蚀的实验结果,重点介绍在InAlAs上面生长InP的湿法选择腐蚀,用HClH∶3PO4C∶H3COOH系列腐蚀液,InPI/nAlAs选择比大于300。InPI/nAlAs湿法选择腐蚀的结果可以很好应用到OEIC芯片制作中,并取得了较好的器件及电路结果。     

Growth of ultrahigh carbon-doped InGaAs and its application toInP/InGaAs(C) HBTs

Growth of ultrahigh carbon-doped p-type InGaAs lattice matched to InP by chemical beam epitaxy (CBE) using carbon tetrabromide (CBr₄ ) as a doping source was investigated. Effects of growth temperature, group V supply pressure, and CBr₄ supply pressure on growth rate, composition, mobility, and hole concentration of carbon-doped InGaAs were studied. Ultrahigh net hole concentration and room-temperature mobility of 2 × 10²⁰/cm³ and 33 cm²/V·sec, respectively, were achieved. Mobility of the ultrahigh carbon-doped InGaAs using CBr₄ compared favorably to those of CBE grown carbon-doped InGaAs using carbon tetrachloride (CCl₄) and molecular beam epitaxy grown beryllium (Be)-doped InGaAs grown at low temperature. The highly carbon-doped InGaAs layers grown by CBE using CBr₄ as a doping source showed a negligible hydrogen passivation effect and were used for the growth of high-performance, highly carbon-doped base InP/InGaAs heterojunction bipolar transistor epitaxial layer structures     

Characteristics of InAlAs/InGaAs high electron mobility transistorsunder 1.3-μm laser illumination

The current-voltage (I-V) characteristics of InAlAs/InGaAs high electron mobility transistors (HEMTs) under illumination are investigated. The change of the drain current caused by the illumination can be explained by using the photovoltaic effect so that the excess holes photo-generated in the InGaAs channel layer accumulate at the source-electrode region and cause an effective decrease in the potential barrier for electrons between the source and the channel. The basic equations describing this phenomenon are derived on the basis of the experimental results. In addition, our experimental results are shown to support the barrier-induced hole pile-up model in which holes generated by the impact ionization accumulate in the InAlAs barrier on the source side and cause the kink effect In InAlAs/InGaAs HEMTs     

InGaAs/InGaAlAs/InAlAs/InP SCH-MQW laser diodes grown by molecular-beam epitaxy

InGaAs/InGaAlAs/InAlAs/InP separate-confinement hetero-structure-multiquantum-well (SCH-MQW) laser diodes have been fabricated by molecular-beam epitaxy (MBE), and room-temperature pulsed operation at 1.57 ?m has been achieved. This SCH-MQW laser is composed of InGaAs well layers, InGaAlAs quaternary barrier layers, and InAlAs and InP cladding layers.     

Electrical properties of InAlAs/InAsxP1-x/InP composite-channel modulation-doped structures grown by solid source molecular beam epitaxy

We report on the electrical characteristics of the two-dimensional electron gas (2DEG) formed in an InAlAs/InAs_xP_1-x/InP pseudomorphic composite-channel modulation-doped (MD) structure grown by solid source (arsenic and phosphorus) molecular beam epitaxy (SSMBE). The As composition, x, of strained InAs_xP_1-x was determined by x-ray diffraction analysis of InP/InAs_xP_1-x/InP multi-quantum wells (MQWs) with compositions of x=0.14 to x=0.72. As the As composition increases, the room temperature sheet resistance of InAlAs/InAs_xP_1-x/InP composite-channel MD structures grown over a range of As compositions decreased from 510 to 250 Ω/cm², resulting from the greater 2DEG confinement and lower electron effective mass in the InAs_xP_1-x channel as x increases. The influence of growth conditions and epitaxial layer designs on the 2DEG mobility and concentration were investigated using 300 K and 77 K Hall measurements. As the exposure time of the As₄ flux on the growth front of InAs_xP_1-x increased during growth interruptions, the 2DEG mobility, in particular the 77K mobility, was considerably degraded due to increased roughness at the InAlAs/InAs_xP_1-x interface. For the InAlAs/InAs_0.6P_0.4/InP composite-channel MD structure with a spacer thickness of 8 nm, the room temperature 2DEG mobility and density were 7200 cm²/Vs and 2.5 × 10¹² cm⁻², respectively. These results show the great potential of the InAlAs/InAs_xP_1-x/InP pseudomorphic composite-channel MD heterostructure for high frequency, power device applications.