FINDINGS. A. Results. Hall Measurements

Transcription

1 FINDINGS REU Student: Matthew Erdman Graduate Student Mentor: Andrew Aragon Faulty Mentor: Luke Lester and Sayan Mukherjee A. Results Hall Measurements Figure 1. Sample R1-55 data from Hall measurement

2 TLM Measurement R1-53 Not ohmi 9.8e-6 5.3e e-5 Not ohmi Not ohmi R1-54 Not ohmi 1.1e-4 3.1e-6 1.5e-5 Not ohmi Not ohmi R1-55 Not ohmi Not ohmi.4e e-4 Not ohmi Not ohmi R1-56 Not ohmi Not ohmi 5.7e-3.6e-3 Not ohmi Not ohmi Table 1: List of ontat resistanes versus annealing temperatures for GaSb /Pd 87Å /Ge 560Å /Au 33Å /Pt 476Å /Au 000Å metallization [1]. R1-53 Not ohmi 4.1e-4 1.e-6 5.4e-5 1.e-4 1.e-3 R1-54 Not ohmi.7e-6 1.1e-6 3.9e-5.9e-4.1e-4 R1-55 Not ohmi 3e-6 1.7e-6 1.e-4 5.7e-4 3.0e-4 R1-56 Not ohmi Not ohmi 1.1e- 1.1e-3 7.3e-3 1.7e- Table : List of ontat resistanes versus annealing temperatures for GaSb /Ni 87Å /Ge 560Å /Au 33Å /Pt 476Å /Au 000Å metallization [1]. (Ω-m ) (Ω-m ) (Ω-m ) (Ω-m ) (Ω-m ) (Ω-m ) R1-53 Not ohmi 1.07e-4 1.5e-4 1.8e-4 4.5e-4 1.0e-3 R1-54 Not ohmi 1.04e-4 1.4e-4.3e-4 3.4e-4 4.0e-4 R1-55 Not ohmi 3.4e-4 3.5e-4 5.6e e-3.0e-3 R1-56 Not ohmi 1.6e-3.4e-3 3.6e-3 7.0e-3 1.1e- Table 3: List of ontat resistanes versus annealing temperatures for GaSb /Ge 560Å /Au 33Å /Pd 87Å /Pt 476Å /Au 000Å metallization [1]. (Ω-m ) (Ω-m ) (Ω-m ) (Ω-m ) (Ω-m ) (Ω-m ) R1-53 Not ohmi 1.1e e e-5 3.3e-4 3.9e-4 R1-54 Not ohmi 5.08e-5 5e-5.7e-5 6.7e-4 6.e-4 R1-55 Not ohmi 1.e-3 1.7e-3 1.4e-3 Not ohmi Not ohmi R1-56 Not ohmi Not ohmi 8.7e-3 7.9e-3 Not ohmi Not ohmi Table 4: List of ontat resistanes versus annealing temperatures for GaSb /Ge 560Å /Au 33Å /Ni 87Å /Pt 476Å /Au 000Å metallization [1].

3 Figure. Plot of measured resistanes as a funtion of ontat separation to alulate and t for n-gasb /Ni 87Å /Ge 560Å /Au 33Å /Pt 476Å /Au 000Å metallization & 45s annealing time [1,] Figure 3. Speifi ontat resistivities (Ohm.m) plotted against anneal temperature (C) for 45 seond anneals for n-gasb /Ni 87Å /Ge 560Å /Au 33Å /Pt 476Å /Au 000Å[1,] Figure 4. Plot of measured resistanes as a funtion of ontat separation to alulate and t for GaSb /Pd 87Å /Ge 560Å /Au 33Å /Pt 476Å /Au 000Å metallization & 45s annealing time [1,] Figure 5. Speifi ontat resistivities (Ohm.m) plotted against anneal temperature (C) for 45 seond anneals for n- GaSb /Pd87Å /Ge 560Å /Au 33Å /Pt 476Å /Au 000Å[1,]

4 Defets, SEM and EDAX Figure 6. EDAX of defet for GaSb grown on SI-GaAs with IMF layer between substrate and MBE growth

5 Figure 7. EDAX of epi layer for GaSb grown on SI-GaAs with IMF layer between substrate and MBE growth B. Conlusions The Hall sample R1-55 was expeted to be n-type due to the intended doping onentration being n-type 1e18. The Hall arrier onentration was alulated to be approximately n-.46e17 m -3. This is within one order of magnitude, whih is within the error of a basi MBE growth proedure. The Hall mobility was alulated to be 365 m /V. This is a onsiderable mobility, but an be improved for this doping level. The resistivity of 7.77e-3 Ω/m is a good expetation, but with further development it may be able to be redued. From the paper, Ohmi ontats to n-type GaSb grown on GaAs by the Interfaial Misfit Disloation tehnique, the ideal annealing temperature was found to be 45 seonds. Further data olleted showed a great suess in forming low resistane ontats from metallizations Pd 87Å /Ge 560Å /Au 33Å /Pt 476Å /Au 000Å and Ni 87Å /Ge 560Å /Au 33Å /Pt 476Å /Au 000Å. This was observed for an annealing temperature of 90 C. The other two metallizations with Ge as the first layer did not show great results in respet to forming low resistane ohmi ontats as did the metallizations with Pd and Ni being the first layer on the GaSb growth. See tables 1-4 for onfirmation of Pd and Ni being the ideal material for the first layer of the ohmi ontat on GaSb. From Figure 3 and Figure 4, the ideal temperature of 90 C was shown to be the ideal annealing temperature. The graph also shows that with very little deviation in temperature, the resistane of the ontats inreased. This data shows that ohmi ontats an be made on n-type

6 GaSb using alloys of both Pd/Ge/Au/Pt/Au and Ni/Ge/Au/Pt/Au with the best results from the samples with Ni/Ge/Au/Pt/Au metallizations. The SEM and EDAX show that the defet was onfirmed to be Ga. This lead to the theory that the ause of the oval defets on the GaSb samples was due to spitting within the MBE hamber. This was further onfirmed with samples that had EDAX performed on them. The EDAX was onfirmed to be set at a orret voltage and urrent level with the epitaxial layer showing the omposition of high purity GaSb. C. Future Work More experiments an be ran on the ohmi ontats to further perfet the alloys and annealing temperatures for high performing ohmi ontats. This is urrently being pursued and more TLM measurements will be onduted shortly to onfirm that the annealing equipment was alibrated orretly. The resistane of the ontats that was olleted will also be onfirmed with further experimentation. Hall samples will be made shortly from GaSb grown on non-intentionally doped GaSb. This will help the team better understand the harateristis of GaSb to further perform studies. A basi TPV will also be made to show a proof of onept implementation of the devie. Defets will ontinued to be studied. This will help better understand the auses of the defets and to make sure all neessary preautions are made to suppress the formation of defets on the material. With the gained knowledge of the Ga spitting, extra steps will be made during MBE growth to ensure high quality material is grown. D. Referenes [1] Rahimi, N., A. A. Aragon, O. S. Romero, D. M. Kim, N. B. Traynor, T. J. Rotter, G. Balakrishnan, S. D. Mukherjee, and L. F. Lester. Ohmi Contats to N-type GaSb Grown on GaAs by the Interfaial Misfit Disloation Tehnique. N.D. Artile. [] Rahimi, Nassim, Andrew A. Aragon, Orlando S. Romero, Matthew K. Erdman, Tom J. Rotter, Ganesh Balakrishnan, Sayan D. Mukherjee, and Luke F. Lester. Ultra-low Resistane NiGeAu and PdGeAu Ohmi Contats On N-GaSb Grown On GaAs. N.d. Artile.