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Abstract:
Work under this contract has focused on a field-assisted 1-2 micronsensitive photoemitter with a reverse biased Ge p-n junction and a thin Cs-O-activated emitting layer of negative electron affinity (NEA) GaAs. The p+-GaAs provides an effective single-crystal low-work-function large-area biasing contact for the Ge p-n junction and allows the n-Ge to be sufficiently thin for optimal performance. Calculations show that some cooling, perhaps to -80 C, will be necessary to reduce the dark current well below the signal level. Detailed theoretical calculations are presented which show that 1-4% quantum efficiency in transmission is possible from either a GaAs/Ge or an InP/Ge device. The optimal design parameters are calculated, and the sensitivity of the parameters is discussed. GaAs/Ge growth using the metal chloride and organometallic vapor phase epitaxy (OM-VPE) methods has been studied in some detail. Only the OM-VPE process results in a true p-GaAs/n-Ge heterojunction essential for our device. The metal chloride process suffers from Ge autodoping into the initial GaAs growth layer. Vacuum activation levels of thick GaAs/Ge have been very high in the reflection mode - comparable to homojunction GaAs/GaAs activation levels. Ultra-thin diffused Ge junctions (less than 1000 A deep) have been successfully fabricated using the OM-VPE method.
| Description: |
Rept. no. 4 (Final), 17 Apr 72-16 Oct 73 |
| Pages: |
67 |
| Report Date: |
06 DEC 1973 |
| Contract Number: |
DAAK0272C0412, ARPAOrder2182 |
| Report Number: |
0474719 |
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