Question: Should I stay in my current role, ask for a pay rise, or find somewhere new?

Situation:
Right now, I'm effectively doing a lead developer role for half the salary of the other member of my team- I'm code reviewing their work (which often has many many errors in it), creating and assigning tickets for both myself and them and engaging in many meetings with senior staff in the company. The other dev in my team has more experience on paper, but the amount of work they are generating is approximately 1/5th of what I produce. I'm really disappointed that when I raised this with my manager & then HR, they have seeming done nothing about the situation. It's really disheartening and it feels as though I'm not really valued.

I don't really have much loyalty to the company, but because I have helped build their internal system from scratch I'd loathe to leave it in the incompetent hands of my colleague (who at present still has a month left of probation).

I can give any further info if you'd like it but I could really do with some advice right now.