Brammertz, G.; Heyns, M.; Newcomb, Simon B.; Afanas'ev, V. V.;Hurley, Paul K.
High mobility III-V substrates with high-k oxides are required for device scaling without loss of channel mobility. Interest has focused on the self-cleaning effect on selected III-V substrates during atomic layer deposition of Al2O3. A thin (∼1 nm) Al2O3 interface control layer is deposited on In0.53Ga0.47As prior to HfO2 growth, providing the benefit of self-cleaning and improving the interface quality by reducing interface state defect densities by ∼50% while maintaining scaling trends. Significant reductions in leakage current density and increased breakdown voltage are found, indicative of a band structure improvement due to the reduction/removal of the In0.53Ga0.47As native oxides.
e REBL program, Office of the CTO, KLA-Tencor Corp., Milpitas, CA 95035, USAWe describe the synthesis, characterization, and application of nanocomposite, tunable resistance coatings consisting of conducting, metallic nanoparticles embedded in an amorphous dielectric matrix. These films are comprised of M:Al 2 O 3 with M=Mo or W, and are prepared by atomic layer deposition (ALD) using alternating exposures to trimethyl aluminum and H 2 O for the Al 2 O 3 ALD and alternating MF 6 /Si 2 H 6 exposures for the metal ALD. By varying the ratio of ALD cycles for the metal and the Al 2 O 3 components in the film, we can tune precisely the resistance of these coatings over a very broad range from 10 5 -10 12 Ohm.cm. These films exhibit ohmic behavior and resist breakdown even at high electric fields of 10 7 V/m. Moreover, the self-limiting nature of ALD allows us to grow these films inside of porous substrates and on complex 3D surfaces. As a result of these qualities, our nanocomposite films have proved exceptional as resistive coatings in microchannel plate electron multipliers and as charge drain coatings in electron-optical devices.
Keywords:Large-area picosecond photodetectors (LAPPD) Time of flight detector Glass capillary array (GCA) Microchannel plate (MCP) Atomic layer deposition (ALD) a b s t r a c tWe present a progress update on plans to establish pilot production and commercialization of Large Area (400 cm 2 ) Picosecond Photodetector (LAPPD ™ ). Steps being taken to commercialize this MCP and LAPPD ™ technology and begin tile pilot production are presented including (1) the manufacture of 203 mm  203 mm borosilicate glass capillary arrays (GCAs), (2) optimization of MCP performance and creation of an ALD coating facility to manufacture MCPs and (3) design, construction and commissioning of UHV tile integration and sealing facility to produce LAPPDs. Taken together these plans provide a "pathway toward commercialization".& 2014 Elsevier B.V. All rights reserved. LAPPDThe Large Area Picosecond Photodetector (LAPPD ™ ) is a microchannel plate (MCP) based photodetector, capable of imaging, and having both high spatial and temporal resolution in a vacuum package with an active area of 400 cm 2 . LAPPD ™ are characterized by a uniquely simple design based upon an all-glass vacuum package comprised of top and bottom plates and square sidewall, each made of borosilicate float glass, depicted in Fig. 1.Key design features of the LAPPD include: (a) an internal chevron pair stack of "next generation" MCPs produced by applying resistive and emissive coatings to borosilicate glass capillary array (GCA) substrates; (b) a modular all-glass detector package with conductive RF microstrips passing through a glass frit seal that hermetically bonds the side walls to the bottom anode plate while allowing electrical contact to the interior of the device; eliminating the need for metal electrical pins penetrating the evacuated detector package; (c) resistively coated spacers that function as high voltage (HV) dividers to distribute voltage across the MCP chevron stack, eliminating the need for separate electrical leads contacting the tops and bottoms of both MCPs; and (d) RF stripline anodes applied to the bottom plate with an analog bandwidth above 1.5 GHz for good spatial and temporal resolution [1]. MCP based photodetectorsMCP's consists of millions of conductive glass capillaries (4-25 mm in diameter) fused together and sliced into a thin plate [2]. Each capillary or channel works as an independent secondary-electron multiplier. Single electrons that hit a pore on one side of the plate convert into large bunches of electrons that cascade from the other side [3], with typical amplification from a pair of plates of 10 7 . Fig. 2 (left) shows a large area glass capillary array (GCA) consisting of millions of 20 mm diameter pores with an overall size of 203 mm  203 mm  1.2 mm with an aspect ratio¼60:1, bias angle of 81, and open area ratio of 60%. Atomic Layer Deposition (ALD) techniques are used to apply resistive and emissive coatings, converting the GCA into a high performance MCP. A high voltage is applied across the top and bottom surfaces of the...
The atomic layer deposition of high dielectric constant oxides like HfO2 on III-V substrates such as In0.53Ga0.47As leads to a poor interface, with the growth of In0.53Ga0.47As native oxides regardless of the surface pretreatment and passivation method. The presence of the native oxides leads to poor gate leakage current characteristics due to the low band gap of the native oxides and the presence of potential wells at the interface. In addition, the poor quality of this interface leads to very large interface state defect densities, which are detrimental to metal-oxide-semiconductor-based device performance. A wide band gap interlayer replacing the native oxide layer would remove the potential wells and provide a larger barrier to conduction. It may also assist in the improvement of the interface quality, but the problem remains as to how this native oxide interlayer cannot only be removed but prevented from regrowing. In this regard, the authors present electrical results showing that the atomic layer deposition (ALD) growth of a thin (∼1 nm) Al2O3 layer before the ALD growth of HfO2 causes a removal/reduction of the native oxides on the surface by a self-cleaning process without subsequent regrowth of the native oxides. As a result, there are significant improvements in gate leakage current densities, and significant improvements in the frequency dispersion of capacitance versus gate voltage, even when a defective In0.53Ga0.47As epitaxial layer on an InP substrate is employed. Measurements at different temperatures confirm that the frequency dispersion is mainly due to interface state defect responses and another weakly temperature dependent mechanism such as border traps, after accounting for the effects of nonideal In0.53Ga0.47As epitaxial layer growth defects where applicable.
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