Whether the reason is as follows? Predominantly HPGe is p type. So compensation of large p type impurity requires more n+ contact. (700um) But n type Ge is made by doping of excess addition of n type impurity in p type HPGe. So n type impurity addition always slightly excess of p type impurity. Hence, slight excess n type impurity in n type HPGe requires, p+ contact with very less thickness. (0.3um)
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1$\begingroup$ Because the n-type region is diffused lithium, and the p-type region is implanted boron. Under reverse bias the depletion region grows dramatically into the n-type region, resulting in a large detection volume. $\endgroup$– Jon CusterCommented Feb 4, 2019 at 14:34
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1$\begingroup$ If the p contact is doped much higher than the n side, then the depletion layer will grow much further into the n region. So, if the p is, say, $10^{18}$ and the n is $10^{15}$, then the n side of the depletion layer is 1000 times wider than the p side. $\endgroup$– Jon CusterCommented Feb 4, 2019 at 15:45
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1$\begingroup$ Lithium is used in silicon and germanium detectors since its diffusion can be driven by biasing the device. There is no way (within reason) that one could diffuse a more normal dopant (B, P, As) over 100's of microns. But with lithium one can get a nice, even doping profile at fairly low levels across millimeters to centimeters. Now, add a highly doped, ion-implanted p++ contact, and you have a great volumetric sensor. Remember, the goal is to make as wide a depletion layer as you can to increase the active volume. $\endgroup$– Jon CusterCommented Feb 4, 2019 at 19:54
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2$\begingroup$ You seem to believe that I exist to answer your question - that is pretty annoying. Look, I've given you plenty of information above about just how gamma detectors work, why you want a thick, lightly doped region to get maximum performance, and why lithium ends up being the dopant of choice. How much clearer do I need to be? $\endgroup$– Jon CusterCommented Feb 5, 2019 at 17:43
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2$\begingroup$ Start with physicstoday.scitation.org/doi/10.1063/1.3037792, then go look at Ortec and Canberra product literature for their detectors. $\endgroup$– Jon CusterCommented Feb 12, 2019 at 14:14
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Read the references as suggested....but still not got answer Li is added by diffusion process but B is added by implantation. In Ion implantation we can achieve thin contact, but in diffusion we can get only Thick contact. Fine. It is liks DJD vs PIPS detector for alpha. Can you tell me why Li is also not added as contact by Ion implantation method?
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1$\begingroup$ FYI, the intention of this forum is that it is a question/answer forum, not a discussion forum. In that respect, this forum is quite different from others that look similar. What you enter in an "Answer" should be a potentially definitive answer. Your comment here can be entered as an edit to your original post, or as a comment. $\endgroup$– garypCommented Mar 18, 2019 at 21:25