Effects of layer design on the performance of InAs/AlSb/GaSb resonant interband tunneling diodes on GaAs substrates

The room temperature current-voltage characteristics of InAs/AlSb/GaSb resonant interband tunneling diodes (RITDs), grown by chemical beam epitaxy on GaAs substrates, are reported as a function of the InAs buffer layer thickness and different interface configurations. The peak-to-valley current ratio (PVCR) improved from 1 to 12 as the buffer thickness was increased from 0 to 500 nm and the density of dislocations caused by the lattice mismatch of ∼7% decreased. No significant improvement was seen for a buffer thickness beyond 500 nm. Dislocation-free RITDs, grown lattice-matched on InAs substrates, show PVCRs of approximately 16. The InAs/AlSb Interfaces in these structures can be either InSb-like or AlAs-like and the interface can have a very strong effect on the diode performance. Unlike the case in InAs/AlSb field effect transistor structures, an AlAs-like interface results in better PVCRs in the diodes. Details of the results of this study are presented.     

Effects of inelastic scattering on interband tunneling inGaSb/AlSb/InAs/GaSb/AlSb/lnAs broken-gap interband tunneling structures

Effects of inelastic scattering on interband tunneling in GaSb/AlSb/InAs/GaSb/AlSb/InAs BGIT's are investigated. The broadening mechanisms due to inelastic scattering are incorporated into the interband tunneling theory. The transmission and reflection coefficients are calculated with the aid of a three-band model, in which the conduction, light-hole, and split-off bands are coupled with one another. It is found that the inelastic scattering lowers the transmission peak and broadens the full-width at half-maximum, resulting in the decrease of the tunneling current. The calculated tunneling current due to inelastic scattering is found to have better agreement with the experiments. In addition, as the valley current plays an important role in the peak-to-valley current ratio (PVR), we then try to deduce the origin of the valley currents. The thermionic current is included in the valley current to estimate the peak-to-valley current ratio. The thermionic component from the GaSb well has important contribution to the valley current in the studied structures. The peak-to-valley current ratio is also estimated and found to have better agreement with the experiment when the inelastic scattering is considered     

Microwave performance and modeling of InAs/AlSb/GaSb resonantinterband tunneling diodes

The microwave frequency performance of InAs/ AlSb/GaSb resonant interband tunneling diodes has been examined experimentally. A bias-dependent small-signal circuit model that matches the measured data well for the full range of measured frequencies (dc to 35 GHz) and the full range of device biases (0 to 0.5 V) has been obtained. To the author's knowledge, this is the first report of a microwave-frequency circuit model that is valid over the full range of device operating biases, including the negative differential resistance region. The bias dependence of the circuit elements contained within the model is examined, and is consistent with device operational principles     

Static random access memories based on resonant interband tunnelingdiodes in the InAs/GaSb/AlSb material system

We have fabricated SRAM's based on resonant interband tunneling diodes in the InAs/AlSb/GaSb material system. The bistability and the switching principles are demonstrated. Numerical simulations of the memory characteristics of the SRAM cell are performed and used for comparing with experiments. Several key issues involving the applications of the device are also discussed     

Sidewall spacer defined resonant interband tunneling diodes

We report on a contacting and fabrication scheme for a sub-500 nm InAs/AlSb/GaSb resonant interband tunneling diode (RITD) without using any fine-line lithography. Epitaxial regrowth on patterned substrates combined with sidewall spacer technology is used to define the device dimensions. During regrowth, the crystal facet termination obtained by choosing the appropriate orientation for the device is utilized to make electrical contact to the device in the desired directions and to isolate the device in all other directions. The concept, fabrication process, current-voltage characteristics of the device, and a comparison with RITDs fabricated in a conventional manner are reported.     

Tri-state logic using vertically integrated Si-SiGe resonant interband tunneling diodes with double NDR

A vertically integrated npnp Si-based resonant interband tunneling diode (RITD) pair is realized with low-temperature molecular beam epitaxy by stacking two RITDs with a connecting backward diode between them. The current-voltage characteristics of the vertically integrated RITD pair demonstrates two sequential negative differential resistance regions in the forward-biasing condition. Tri-state logic is demonstrated by using the vertically integrated RITDs as the drive and an off-chip resistor as the load.     

RF performance and modeling of Si/SiGe resonant interband tunneling diodes

The RF performance of two different Si-based resonant interband tunneling diodes (RITD) grown by low-temperature molecular beam epitaxy (LT-MBE) were studied. An RITD with an active region of B /spl delta/-doping plane/2 nm i-Si/sub 0.5/Ge/sub 0.5//1 nm i-Si/P /spl delta/-doping plane yielded a peak-to-valley current ratio (PVCR) of 1.14, resistive cutoff frequency (f/sub r0/) of 5.6 GHz, and a speed index of 23.3 mV/ps after rapid thermal annealing at 650/spl deg/C for 1 min. To the authors' knowledge, these are the highest reported values for any epitaxially grown Si-based tunnel diode. Another RITD design with an active region of 1 nm p+ Si/sub 0.6/Ge/sub 0.4//B /spl delta/-doping plane/4-nm iSi/sub 0.6/Ge/sub 0.4//2 nm i-Si/P /spl delta/-doping plane and annealed at 825/spl deg/C for 1 min had a PVCR of 2.9, an f/sub r0/ of 0.4 GHz, and a speed index of 0.2 mV/ps. A small signal model was established to fit the measured S/sub 11/ data for both device designs. Approaches to increase f/sub r0/ are suggested based on the comparison between these two diodes. The two devices exhibit substantially different junction capacitance/bias relationships, which may suggest the confined states in the /spl delta/-doped quantum well are preserved after annealing at lower temperatures but are reduced at higher temperature annealing. A comprehensive dc/RF semi-physical model was developed and implemented in Agilent advanced design system (ADS) software. Instabilities in the negative differential resistance (NDR) region during dc measurements were then simulated.     

Investigation of negative differential resistance phenomena inGaSb/AlSb/InAs/GaSb/AlSb/InAs structures

The negative differential resistance (NDR) phenomena were observed in GaSb/AlSb/InAs/-GaSb/AlSb/InAs resonant interband tunnel structures. Electrons have resonantly achieved interband tunneling through the InAs/GaSb broken-gap quantum well. The InAs well width causes significant variations of the peak current density and NDR behaviors. The peak current density varies exponentially with the AlSb barrier thickness. The multiple NDR behavior was observed with appropriate InAs well and AlSb barrier thicknesses, e.g., 30 Å thick AlSb barrier and 240 Å wide InAs well. Only single negative resistance has, otherwise, been seen. The three-band model was used to interpret the effect of the InAs well and AlSb barrier on the current-voltage characteristics of GaSb/AlSb/InAs/GaSb/AlSb/InAs structures     

Population inversion in two-dimensional InAs/GaSb/AlSb systems

We analyse the potentiality of InAs/GaSb/AlSb tunnel structures for creation of the population inversion and stimulated radiation both in the presence and in the absence of magnetic field.     

GaSb Schottky diodes for infrared detectors

GaSb Schottky barrier photodiodes are shown to have quantum efficiency higher than 35 percent over a broad band of infra-red light wavelength shorter than 1.6 µm. Theoretical calculations of current voltage characteristics including tunneling current are compared with the experiment and it is suggested that surface leakage current, tunneling current, and avalanche breakdown, respectively, dominate the reverse characteristics with increasing voltage. Epitaxial growth of an n-type layer with carrier density 10¹⁵cm^-3and suitable surface passivation are key technologies for the application of this material to infra-red detectors.     

Investigation of the influence of the well and the barrierthicknesses in GaSb/AlSb/GaSb/AlSb/InAs double-barrier interbandtunneling structures

The tunneling currents of GaSb/AlSb/GaSb/AlSb/InAs double-barrier interband tunneling (DBIT) structures were studied experimentally by varying the thickness of the well and the barrier layers systematically. The optimal thicknesses for the GaSb well and the AlSb barriers were found to be 6.5 and 1.0 nm, respectively, to obtain a high peak current density (19 kA/cm²), with a large peak-to-valley ratio of 4. The high peak current in the DBIT structure shows the strong effect of the resonant coherence of the wave function across the double barrier. For the case of a small GaSb well width (3 nm), a drastic reduction of the peak current was observed, an effect suggesting that the electron-wave function in the InAs couples primarily to the quantized light hole state in the GaSb well     

A complementary heterostructure field effect transistor technologybased on InAs/AlSb/GaSb

A complementary heterojunction field effect transistor technology based on the InAs/AlSb/GaSb system is proposed. The structure is formed by the vertical integration of InAs n-channel and GaSb p-channel HFET devices. The superior transport properties of electrons in InAs and holes in GaSb and their band offsets to AlSb or AlSbAs yield devices with transconductances much greater than AlGaAs/GaAs n- and p-channel HFETs. It is shown that a complementary circuit fabricated from these devices could provide room-temperature performance up to six times greater than that predicted for AlGaAs/GaAs complementary circuits     

InP-base resonant tunneling diodes

We have fabricated Ino.53Ga0.47As/AlAs/InP resonant tunneling diodes (RTDs) based on the air-bridge technology by using electron beam lithography processing. The epitaxial layers of the RTD were grown on semiinsulating (100) InP substrates by molecular beam epitaxy. RTDs with a peak current density of 24.6 kA/cm2 and a peak-to-valley current ratio of 8.6 at room temperature have been demonstrated.     

InP基共振遂穿二极管器件（RTD）研究

我们在实验中对InGaAs/AlAs/InP共振遂穿二极管（RTD）材料结构进行了优化设计,并用MBE设备在(100)半绝缘InP单晶片上生长了RTD外延材料。我们采用电子束光刻工艺和空气桥互连技术,制作了InP基RTD器件。并在室温下测试了器件的电学特性：峰值电流密度24.6kA/cm2,峰谷电流比(PVCR)为8.6。     

1.7-ps, microwave, integrated-circuit-compatible InAs/AlSb resonanttunneling diodes

Microwave integrated-circuit-compatible InAs/AlSb resonant tunneling diodes (RTDs) have been fabricated. The resulting devices have peak current densities of 3.3×10⁵ A/cm² with peak-to-valley ratios of 3.3. Switching transition times of 1.7 ps are measured using electrooptic sampling techniques     

Unintentional As incorporation in molecular beam epitaxially grown InAs/AlSb/GaSb heterostructures

We investigate unintentional arsenic incorporation during the molecular-beam epitaxial growth of AlSb/InAs/GaSb heterostructures, using both a standard As₄ evaporation cell and a valved arsenic cracker. When a standard As₄ cell is used, unintentional arsenic concentrations as large as 10–20% can be incorporated into the AlSb and GaSb layers from the background As ambient in the growth chamber, both during growth and on stationary surfaces. This incorporation can be controlled and suppressed with the use of a valved As cracker. Suppression of the As background substantially improves the electrical transport properties of AlSb/InAs/AlSb quantum well structures.     

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     

Low-parasitic, planar Schottky diodes for millimeter-waveintegrated circuits

The design and fabrication of air-bridged, ultra-low-capacitance Schottky barrier diodes are described. Mott diodes, for mixer applications, and varactor diodes, for use in frequency multipliers, have been produced simultaneously on epitaxial wafers grown by molecular beam epitaxy. Typical mixer diodes have a nominal anode contact area of 4 μm² and exhibit a total zero-bias capacitance of 4.0-4.5 fF (including a parasitic capacitance of approximately 1.0 fF) and a series resistance of 6-8 Ω. Diode chips have been incorporated in hybrid integrated circuit (MIC) mixers for 33-50 GHz and 75-110 GHz and an MIC frequency tripler for 90-140 GHz. Fully monolithic (MMIC) subharmonically pumped mixers for 75-110 GHz have also been fabricated and tested     

Diffusion barrier cladding in Si/SiGe resonant interband tunneling diodes and their patterned growth on PMOS source/drain regions

Si/SiGe resonant interband tunnel diodes (RITDs) employing /spl delta/-doping spikes that demonstrate negative differential resistance (NDR) at room temperature are presented. Efforts have focused on improving the tunnel diode peak-to-valley current ratio (PVCR) figure-of-merit, as well as addressing issues of manufacturability and CMOS integration. Thin SiGe layers sandwiching the B /spl delta/-doping spike used to suppress B out-diffusion are discussed. A room-temperature PVCR of 3.6 was measured with a peak current density of 0.3 kA/cm/sup 2/. Results clearly show that by introducing SiGe layers to clad the B /spl delta/-doping layer, B diffusion is suppressed during post-growth annealing, which raises the thermal budget. A higher RTA temperature appears to be more effective in reducing defects and results in a lower valley current and higher PVCR. RITDs grown by selective area molecular beam epitaxy (MBE) have been realized inside of low-temperature oxide openings, with performance comparable with RITDs grown on bulk substrates.     

Well-defined electrical properties of high-strain resonant interband tunneling structure

The GaAs/InAs high-strain resonant interband tunneling diodes (HSRITDs) have been implemented by metal organic chemical vapor deposition (MOCVD). The current-voltage characteristics of variable quantum well and barrier thickness grown on (1 1 1) GaAs substrates are investigated. Experimental results reveal that the quantum barrier and well layer will influence current-voltage properties such as the peak current density, valley current density, and peak-to-valley current ratio (PVCR). Both peak current and valley current density decrease with increasing layers width. This result also exhibits the variation of PVCR with layers width.