There are two main strategies to make the home page rank higher than its sub-pages: on-page SEO on off-page SEO.
Unless the search phrase you are targeting is competitive, just a little nudge to Google might get your homepage ranking.
For on-screen SEO, you would add key textual content to the homepage, and perhaps do other things like add a hCard.
For off-screen SEO, you would leverage links from other pages to convince Google the home page is the authoritative page. You can do this with your internal linking, by putting your targeted keywords into the anchor text of the links to the home page.
You can also work to get other websites to link to the homepage, and aiming to get the targeted keywords in your anchor text. Some websites (like StackExchange) will allow you to have a link to your home page — and this will have some effect, if the links do not have the "nofollow" tag — whether they have nofollow varies by website.
One other technique you might try is putting a canonical URL tag on your about page that points to the home page URL. This could be useful if your home page has equivalent content to the about page, but represented in a less SEO-friendly way (e.g., inside graphics). You are basically saying, “These pages are equivalent, but please send users to this one.” If that’s not really true, then use this technique at your own risk — “tricking” Google is a dangerous game to play for SEO.
But ask yourself if Google has a point
If the information the user would want is on your about page, and not on your home page, shouldn’t you change that?