Publications

Armstrong, Andrew A.; Douglas, Erica A.; Klein, Brianna A.; Baca, A.G.; Crawford, Mary H.; Allerman, A.A.; vizkelethy, george v.; Carey IV, P.C.; Ren, F.R.; Pearton, S.J.P.; Jackson, Christine J.; Arehart, Aaron R.; Ringel, Steve R.

Abstract not provided.

Journal of Vacuum Science and Technology B

Henry, Michael D.; Young, Travis R.; Douglas, Erica A.; Griffin, Benjamin G.

Substitution of Al by Sc has been predicted and demonstrated to improve the piezoelectric response in AlN for commercial market applications in radio frequency filter technologies. Although cosputtering with multiple targets have achieved Sc incorporation in excess of 40%, industrial processes requiring stable single target sputtering are currently limited. A major concern with sputter deposition of ScAl is the control over the presence of non-c-axis oriented crystal growth, referred to as inclusions here, while simultaneously controlling film stress for suspended microelectromechanical systems (MEMS) structures. This work describes 12.5% ScAl single target reactive sputter deposition process and establishes a direct relationship between the inclusion occurrences and compressive film stress allowing for the suppression of the c-axis instability on silicon (100) and Ti/TiN/AlCu seeding layers. An initial high film stress, for suppressing inclusions, is then balanced with a lower film stress deposition to control total film stress to prevent Euler buckling of suspended MEMS devices. Contour mode resonators fabricated using these films demonstrate effective coupling coefficients up to 2.7% with figures of merit of 42. Furthermore, this work provides a method to establish inclusion free films in ScAlN piezoelectric films for good quality factor devices.

Journal of Vacuum Science and Technology B

Henry, Michael D.; Young, Travis R.; Douglas, Erica A.; Griffin, Benjamin G.

Substitution of Al by Sc has been predicted and demonstrated to improve the piezoelectric response in AlN for commercial market applications in radio frequency filter technologies. Although cosputtering with multiple targets have achieved Sc incorporation in excess of 40%, industrial processes requiring stable single target sputtering are currently limited. A major concern with sputter deposition of ScAl is the control over the presence of non-c-axis oriented crystal growth, referred to as inclusions here, while simultaneously controlling film stress for suspended microelectromechanical systems (MEMS) structures. In this paper, we describe 12.5% ScAl single target reactive sputter deposition process and establishes a direct relationship between the inclusion occurrences and compressive film stress allowing for the suppression of the c-axis instability on silicon (100) and Ti/TiN/AlCu seeding layers. An initial high film stress, for suppressing inclusions, is then balanced with a lower film stress deposition to control total film stress to prevent Euler buckling of suspended MEMS devices. Contour mode resonators fabricated using these films demonstrate effective coupling coefficients up to 2.7% with figures of merit of 42. Finally, this work provides a method to establish inclusion free films in ScAlN piezoelectric films for good quality factor devices.

Esteves, Giovanni E.; Berg, Morgann B.; Henry, Michael D.; Griffin, Benjamin G.; Douglas, Erica A.

Abstract not provided.

Allerman, A.A.; Armstrong, Andrew A.; Crawford, Mary H.; Pickrell, Gregory P.; Baca, A.G.; Klein, Brianna A.; Douglas, Erica A.; Dickerson, Jeramy R.; Flicker, Jack D.; Neely, Jason C.; Kaplar, Robert K.

Abstract not provided.

Jones, Adam J.; Klein, Brianna A.; Baca, Albert O.; Armstrong, Andrew A.; Allerman, A.A.; Douglas, Erica A.

Abstract not provided.

Allerman, A.A.; Armstrong, Andrew A.; Crawford, Mary H.; Pickrell, Gregory P.; Baca, A.G.; Klein, Brianna A.; Douglas, Erica A.; Dickerson, Jeramy R.; Kaplar, Robert K.

Abstract not provided.

Esteves, Giovanni E.; Berg, Morgann B.; Henry, Michael D.; Griffin, Benjamin G.; Douglas, Erica A.

Abstract not provided.

Klein, Brianna A.; Douglas, Erica A.; Armstrong, Andrew A.; Allerman, A.A.; Abate, Vincent M.; Baca, A.G.

Abstract not provided.

Armstrong, Andrew A.; Douglas, Erica A.; Klein, Brianna A.; Baca, A.G.; Fortune, Torben R.; Allerman, A.A.; Abate, Vincent M.

Abstract not provided.

Martinez, Marino M.; King, Michael P.; Baca, A.G.; Allerman, A.A.; Armstrong, Andrew A.; Klein, Brianna A.; Douglas, Erica A.; Kaplar, Robert K.; Swanson, Scot E.

Abstract not provided.

Dickens, Peter D.; Gunning, Brendan P.; Armstrong, Andrew A.; Klein, Brianna A.; Douglas, Erica A.; Gastian, Loren G.; Atcitty, Stanley A.; Maria, Jon-Paul M.; Ihlefeld, Jon F.; Paisley, Elizabeth A.

Abstract not provided.

Henry, Michael D.; Young, Travis R.; Douglas, Erica A.; Esteves, Giovanni E.; Griffin, Benjamin G.

Abstract not provided.

ECS Journal of Solid State Science and Technology

Baca, A.G.; Klein, Brianna A.; Allerman, A.A.; Armstrong, Andrew A.; Douglas, Erica A.; Stephenson, Chad A.; Fortune, Torben R.; Kaplar, Robert K.

AlGaN-channel high electron mobility transistors (HEMTs) are among a class of ultra wide-bandgap transistors that are promising candidates for RF and power applications. Long-channel Al_xGa_1-xN HEMTs with x = 0.7 in the channel have been built and evaluated across the -50°C to +200°C temperature range. These devices achieved room temperature drain current as high as 46 mA/mm and were absent of gate leakage until the gate diode forward bias turn-on at ~2.8 V, with a modest -2.2 V threshold voltage. A very large I_on/I_off current ratio, of 8 × 10⁹ was demonstrated. A near ideal subthreshold slope that is just 35% higher than the theoretical limit across the temperature range was characterized. The ohmic contact characteristics were rectifying from -50°C to +50°C and became nearly linear at temperatures above 100°C. An activation energy of 0.55 eV dictates the temperature dependence of off-state leakage.

Kaplar, Robert K.; Allerman, A.A.; Armstrong, Andrew A.; Crawford, Mary H.; Pickrell, Gregory P.; Dickerson, Jeramy R.; Flicker, Jack D.; Neely, Jason C.; King, Michael P.; Cross, Karen C.; Glaser, Caleb E.; Van Heukelom, Michael V.; Baca, A.G.; Reza, Shahed R.; Klein, Brianna A.; Douglas, Erica A.

Abstract not provided.

Douglas, Erica A.; Brumbach, Michael T.; Paisley, Elizabeth A.; Klein, Brianna A.; Baca, A.G.; Allerman, A.A.; Armstrong, Andrew A.

Abstract not provided.

Kaplar, Robert K.; Allerman, A.A.; Armstrong, Andrew A.; Crawford, Mary H.; Pickrell, Gregory P.; Dickerson, Jeramy R.; Flicker, Jack D.; Neely, Jason C.; King, Michael P.; Cross, Karen C.; Glaser, Caleb E.; Van Heukelom, Michael V.; Baca, A.G.; Reza, Shahed R.; Klein, Brianna A.; Douglas, Erica A.

Abstract not provided.

Henry, Michael D.; Timon, Robert P.; Young, Travis R.; Douglas, Erica A.; Griffin, Benjamin G.

Abstract not provided.

Kaplar, Robert K.; Allerman, A.A.; Crawford, Mary H.; Pickrell, Gregory P.; Dickerson, Jeramy R.; Armstrong, Andrew A.; King, Michael P.; Baca, A.G.; Klein, Brianna A.; Douglas, Erica A.; Flicker, Jack D.; Neely, Jason C.

Abstract not provided.

Allerman, A.A.; Crawford, Mary H.; Pickrell, Gregory P.; Armstrong, Andrew A.; Baca, A.G.; Kaplar, Robert K.; Dickerson, Jeramy R.; Klein, Brianna A.; Douglas, Erica A.; King, Michael P.; Van Heukelom, Michael V.

Abstract not provided.

International Conference on Optical MEMS and Nanophotonics

Grine, Alejandro J.; Siddiqui, A.; Keeler, Gordon A.; Shaw, M.J.; Eichenfield, Matthew S.; Friedmann, Thomas A.; Douglas, Erica A.; Wood, M.G.; Dagel, D.J.; Hains, C.; Koch, L.F.; Nordquist, C.D.; Serkland, Darwin K.

We propose and theoretically analyze a new cavity optomechanical oscillator gyroscope. Mechanical frequency acts as a sensitive readout of rotation through the optomechanical spring and Sagnac effects. Remarkably, reducing device size improves scale factor.

ECS Journal of Solid State Science and Technology

Klein, Brianna A.; Baca, A.G.; Armstrong, Andrew A.; Allerman, A.A.; Sanchez, Carlos A.; Douglas, Erica A.; Crawford, Mary H.; Miller, Mary A.; Kotula, Paul G.; Fortune, Torben R.; Abate, Vincent M.

Here, we present a low resistance, straightforward planar ohmic contact for Al_0.45Ga_0.55N/Al_0.3Ga_0.7N high electron mobility transistors. Five metal stacks (a/Al/b/Au; a = Ti, Zr, V, Nb/Ti; b = Ni, Mo, V) were evaluated at three individual annealing temperatures (850, 900, and 950°C). The Ti/Al/Ni/Au achieved the lowest specific contact resistance at a 900°C anneal temperature. Transmission electron microscopy analysis revealed a metal-semiconductor interface of Ti-Al-Au for an ohmic (900°C anneal) and a Schottky (850°C anneal) Ti/Al/Ni/Au stack. HEMTs were fabricated using the optimized recipe with resulting contacts that had room-temperature specific contact resistances of ρ_c = 2.5 × 10^-5 Ω cm², sheet resistances of R_SH = 3.9 kΩ/$\blacksquare$, and maximum current densities of 75 mA/mm (at VGATE of 2 V). Electrical measurements from -50 to 200°C had decreasing specific contact resistance and increasing sheet resistance, with increasing temperature. These contacts enabled state-of-the-art performance of Al_0.45Ga_0.55N/Al_0.3Ga_0.7N HEMTs.

Sharma, Peter A.; Douglas, Erica A.; Henry, Michael D.; Lewis, Rupert; Harris, Charles T.; Wiwi, Michael W.; Smith, Sean S.; Lima-Sharma, Ana L.; Brumbach, Michael T.; Sugar, Joshua D.

Abstract not provided.

Klein, Brianna A.; Baca, A.G.; Armstrong, Andrew A.; Allerman, A.A.; Douglas, Erica A.; Sanchez, Carlos A.; Kotula, Paul G.; Miller, Mary A.; Reza, Shahed R.

Abstract not provided.

Allerman, A.A.; Baca, A.G.; Armstrong, Andrew A.; Dickerson, Jeramy R.; King, Michael P.; Kaplar, Robert K.; Douglas, Erica A.; Klein, Brianna A.; Sanchez, Carlos A.

Abstract not provided.