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We report on our work on the double electron layer tunneling transistor (DELTT), based on the gate-control of two-dimensional --two-dimensional (2D-2D) tunneling in a double quantum well heterostructure. While previous quantum transistors have typically required tiny laterally-defined features, by contrast the DEL'IT is entirely planar and can be reliably fabricated in large numbers. We use a novel epoxy-bond-and-stop-etch (EBASE) flip-chip process, whereby submicron gating on opposite sides of semiconductor epitaxial layers as thin as 0.24 microns can be achieved. Because both electron layers in the DELTT are 2D,the resonant tunneling features are unusually sharp, and can be easily modulated with one or more surface gates. We demonstrate DELTTs with peak-to-valley ratios in the source-drain I-V curve of order 20:1 below 1 K. Both the height and position of the resonant current peak can be controlled by gate voltage over a wide range. DELTTs with larger subband energy offsets (-21 meV) exhibit characteristics that are nearly as good at 77 K, in good agreement with our theoretical calculations. Using these devices, we also demonstrate bistable memories operating at 77 DISCLAIMERThis report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. DISCLAIMERPortions of this document may be illegible in electronic image products. Images are produced from the best available original document. 2 K.in gain, and high-speed.Finally, we briefly discuss the prospects for room temperature operation, increases 3 INTRODUCTIONElectronic devices based on resonant tunneling in semiconductor heterostructures have seen considerable effort ever since Tsu and Esaki' proposed the double barrier resonant tunneling diode (DBRTD) in 1973. The device was shortly thereafter demonstrated by Chang, Esaki, and Tsu2. In the DBRTD, typically grown in the GaAs/Al,Ga,-,As material system, electrons in a three-dimensional (3D) emitter layer can pass into a 3D collector layer only by first resonantly tunneling through two-dimensional (2D) electron states which are confined in a quantum well (QW) between two narrow barriers. To first order, electrons can tunnel only when their energy and in-plane momentum are conserved3. As a voltage is applied between the emi...

While the low cost and strong safety record of lead-acid batteries make them an appealing option compared to lithium-ion technologies for stationary storage, they can be rapidly degraded by the extended periods of high rate, partial state-of-charge operation required in such applications. Degradation occurs primarily through a process called hard sulfation, where large PbSO 4 crystals are formed on the negative battery plates, hindering charge acceptance and reducing battery capacity. Various researchers have found that the addition of some forms of excess carbon to the negative active mass in lead-acid batteries can mitigate hard sulfation, but the mechanism through which this is accomplished is unclear. In this work, the effect of carbon composition and morphology was explored by characterizing four discrete types of carbon additives, then evaluating their effect when added to the negative electrodes within a traditional valve-regulated lead-acid battery design. The cycle life for the carbon modified cells was significantly larger than an unmodified control, with cells containing a mixture of graphitic carbon and carbon black yielding the greatest improvement. The carbons also impacted other electrochemical aspects of the battery (e.g., float current, capacity, etc.) as well as physical characteristics of the negative active mass, such as the specific surface area. Valve-regulated lead-acid (VRLA) batteries are a mature rechargeable energy storage technology. Low initial cost, well-established manufacturing base, proven safety record, and exceptional recycling efficiency make VRLA batteries a popular choice for emerging energy storage needs.1,2 VRLA batteries are employed in stationary storage applications such as: utility ancillary regulation services, wind farm energy smoothing, and solar photovoltaic energy smoothing.3 Stationary applications may require short duration, high-rate, and partial state-of-charge cycling (HRPSoC). 4 Under HRPSoC duty, conventional VRLA cells fail prematurely from irreversible PbSO 4 formation within the negative plates.5 Regular cycling to 100% state-of-charge (SoC) mitigates PbSO 4 crystal formation and growth. However, regularly cycling to 100% SoC is not viable for many stationary storage applications. Large PbSO 4 crystals are not easily reduced back to metallic lead during HRPSoC charging, reducing cycle life. Reduced cycle life of VRLA batteries increases the operating cost, thereby limiting their practicality for stationary applications.VRLA battery HRPSoC cycle life can be increased with carbon modification of the negative active material (NAM).6-10 Adding carbon to the negative plate inhibits PbSO 4 crystal formation and/or limits PbSO 4 crystal growth.11-13 The underlying mechanism responsible for reducing PbSO 4 formation/accumulation is dependent on the size of the PbSO 4 crystallites. Controlling PbSO 4 microstructure has been found to be difficult while maintaining low cost. Other methods exist to limit PbSO 4 crystal size; including utilization of a carbon honeyco...

We demonstrate a novel quantum device, the double electron layer tunneling transistor (DEL'IT). The DEL'lT's operating principle is based on the gate-control of 2D-2D resonant tunneling between the two electron layers in an AlGaAs/GaAs double quantum well heterostructure. Unlike other quantum transistors, the DEL'IT does not require small lateral dimensions, but is entirely planar in configuration, enabling ease in fabrication. We demonstrate static memories at 77 K, and unipolar complementary static memories at 1.5 K, using half as many transistors as conventionally required.

We describe the first demonstration of dual-side electron beam lithography in achieving independent submicron gating in double quantum well devices. The technique utilizes the epoxy-bond and stop-etch process to remove the substrate material which allows the backside gates to be placed in close proximity (less than 1 µm) to the frontside gates. The use of electron beam lithography allows both the definition of submicron features and the precise alignment of the front and back features to each other. We have applied this technique to the fabrication of double quantum point contacts on coupled AlGaAs/GaAs double quantum wells. Low-temperature transport measurements clearly show the formation of coupled, independently controllable mesoscopic structures in each of the two quantum wells.