n+ contact of p type Ge is ~700µm thick compared to p+ contact of n type Ge only ~0.3µm. The process of adding the contact is different. n+ contact Li is added by diffusion process but p+ contact B is added by ion implantation technique. In diffusion we can get only thick contact but in ion implantation we can achieve thin contact, Fine. With a thin (~0.3µm) Li ion implantation, low energy efficiency of p type HPGe detector can be on par with n type HPGe detector (as per the attached fig).

Why Li is also not added as contact by ion implantation method? Is it a mandatory requirement of having thick (~700µm) n+ contact or only due to technology used for doping, we are getting thick (~700µm) contact?