Is it a good idea to upload rejected papers in arXiv? I have a few earlier works which have been rejected from conferences and journals in the past (last 6 months). Now, I and my co-authors are not interested in submitting elsewhere and have no idea on how to improve these papers.

I was thinking, will it be a good idea to upload these papers in arXiv? Will it create any wrong impression in the community? Will it have bad impact on my profile?
Yes, you should upload them. 

If you think the works are good and worth reading, but don't see a good opportunity to publish them in a journal or at a conference, then the arXiv is the way to go. Actually, many people have unpublished manuscripts and even some influential work only exists as technical report or preprint. It's not uncommon. 

If it would be worth it to pursue "real publication" is a different question...