Voltage-controlled current sources (VCCS) can be used when we need to model a device or any part having voltage as input and current as output. Same is the case for voltage-controlled voltage sources (VCVS).
Now, what should be my strategy when I want to model some device in ORCAD PSPICE having the output as capacitor or carrier concentration other than voltage and current?
Use a BV Behavioral voltage source. I once simulated an entire sigma delta converter with it. And like Lorenzo already said, this is based on, in my opinion a more useful simulator LTspiceIV.
I don't know PSPICE too well, but if you are not constrained by that specific simulator and you are willing to use LTspice (more details here), you can make use of a combination of behavioral sources and passive elements.
For more details on behavioral sources in LTspice see this answer of mine.
Anyway, it may well be that also PSPICE has analogous support for behavioral sources, so search its guide and see what capabilities it offers.
However, unless you are forced to use PSPICE for some reason, I strongly suggest you use LTspice instead, especially because it has no limitation on the number of parts like the free version of PSPICE (assuming you are not using a full-featured version of PSPICE).
It has been decades since I used PSPICE so I can't comment on it's current capabilities. For simulation I use Cadence Spectre and this simulator supports VerilogA modeling. In VerilogA you can model almost anything you want by just describing the behaviour that you want. I have no idea if PSPICE can handle VerilogA or anything like it.
All commonly used simulation packages (PSpice, LTSpice, Superspice, TopSpice,....) contain realistic macromodels (for transistors, opamps,...) which cosists of a combination of controlled sources and a variety of passive components. That means, I see no reasons why you shouldn`t create some similar models of your own.
