A private equity firm is planning a massive mixed-use complex in Conyers that would include more than 1,400 new housing units partly aimed at new employees at the Baxter International plant down the road.

The firm, called 4A International LLC, filed papers with the state on Thursday signaling plans to build on a 308-acre site in Conyers off I-20. Contractors could break ground as early as late 2013, and it could be finished by 2023. The first phase could be complete by early as 2015.

The plans would involve about 1,400 residential units — apartments and single-family houses — and more than 500,000 square feet of retail and office space. About a quarter of the land could be set aside for green space and other recreational uses, said David Roper, a manager with the company. The total project could range between $300 million and $400 million.

Baxter announced plans earlier this year to build a $1 billion pharmaceutical manufacturing plant about 12 miles down the road in Social Circle that would employ 1,500 people by 2018. The housing market in the surrounding area remains particularly tight, with record-low supply and little new construction planned.

Mixed-use projects have taken a beating during the economic downturn. A portion of Atlantic Station was sold off by insurance giant AIG, and developers scaled back proposals for the Streets of Buckhead project and the Avalon development in Alpharetta.

The plans for the Conyers complex are still taking shape, and Roper said it’s too early to detail many specifics. But he said engineers envision dividing the land into four different zones. One would be predominantly commercial, the second would house apartments, the third would be single-family homes and the fourth would have parks and other amenities.

“It’s very ambitious, but we have high hopes,” Roper said. “We think the I-20 east corridor will continue to grow with the Baxter housing market.”