Nearly five months after Steve Ballmer's announcement of his departure as Microsoft's CEO, the company's board is considering Ericsson chief executive Hans Vestberg as a replacement, according to anonymous Bloomberg sources close to the recruitment process.

Microsoft said they plan to pick a successor by summer 2014, but a December blogpost by independent director John Thompson – who is leading the search – suggested he wanted the decision to be made early this year.

Vestberg has been chief of the Swedish technology company since January 2010, overseeing a 19% rise in the company's share price. At 48, he is nearly a decade younger than Ballmer, who planned to leave Microsoft within a year after his announcement on 23 August.

Thompson said that the candidate shortlist has been narrowed down to 20 names. Other names thought to be on the list include Satya Nadella, Microsoft cloud-computing head, and Nokia CEO Stephen Elop.

The search for a replacement is said to have been complicated by the dominating personalities of co-founders Bill Gates and Steve Ballmer on the board. The Wall Street Journal reported that the potential for boardroom clashes has been a turnoff for candidates.

Ford CEO Alan Mulally, 68, was under consideration for the post, but announced last week that he would stay at the car manufacturer.